DRAFT ENVIRONMENTAL IMPACT STATEMENT TRAFFIC AND RECREATIONAL MANAGEMENT

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP89-00244R001002410011-7
• Release Decision: RIFPUB
• Original Classification: K
• Document Page Count: 137
• Document Creation Date: December 22, 2016
• Document Release Date: May 17, 2010
• Sequence Number: 11
• Publication Date: September 27, 1985
• Content Type: REPORT

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draft environmental impact statement
traffic and recreational management
`;C" 2 `? "7 1985
MEMORIAL PARKWAY/ VIRGINIA-MARYLAND-DISTRICT OF COLUMBIA
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DRAFT ENVIRONMENTAL IMPACT STATEMENT
for
TRAFFIC AND RECREATIONAL MANAGEMENT
GEORGE WASHINGTON MEMORIAL PARKWAY
(Spout Run to Theodore Roosevelt Bridge)
and
SPOUT RUN PARKWAY
Virginia-Maryland-District of Columbia
Four alternatives are considered for improving traffic flow and safety on
the study sections of the parkways. The alternatives range from minor
safety improvements on the existing roadway to major structural changes.
All questions concerning the contents of this document should be directed
to
Keith Dunbar
National Park Service
Denver Service Center THE
P. 0. Box 25287
Denver, Colorado 80225
[phone]
Comments on this document are due by NOV 2 6 11985,
and should be sent to
John F. Byrne, Superintendent
George Washington Memorial Parkway
c/o Turkey Run Park
McLean, Virginia 22101
[phone]
Prepared by
U.S. Department of the Interior / National Park Service
in coordination with
Federal Highway Administration / Eastern Direct Federal Division
Commonwealth of Virginia / Department of Highways and Transportation
Arlington County, Virginia / Department of Public Works
District of Columbia / Department of Public Works
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SUMMARY
George Washington Memorial Parkway, established by Congress in 1930, is
a major unit of the national capital park system. It serves as a scenic
gateway to Washington, D.C., and contains or connects numerous
monuments, historic sites, and recreation areas in Virginia, Maryland,
and the District of Columbia. The parkway and related sites form a
valuable greenbelt along the Potomac River through much of the
Washington metropolitan area.
The National Park Service is studying solutions to commuter traffic
congestion and safety problems along the section of the GWMP roadway
between Theodore Roosevelt Memorial Bridge and Spout Run Parkway and
on Spout Run Parkway. Traffic levels are at capacity on the inbound
lanes during the morning rush hours and on the outbound lanes during
the evening rush hours. Traffic backups are common during the morning
rush hours at the intersection of Spout Run Parkway and inbound GWMP
and on the off-ramp to Roosevelt Bridge. During the evening rush
hours, traffic congestion occurs on the on-ramps from Roosevelt and Key
bridges and on the section of GWMP between Key Bridge and the Spout
Run exit. The accident rate for this portion of GWMP within the study
area, although not excessive, is higher than the rate for other sections
of the parkway.
In seeking solutions to these commuter traffic problems, the National Park
Service must also fulfill its responsibilities to preserve and protect the
scenic, natural, cultural, and recreational values of the parkway. The
study area section of the parkway is a narrow band of parkland tucked
between Arlington and the Potomac River, and it is extremely susceptible
to the loss of its parklike character if its thin vegetative buffer is
disturbed.
Four alternatives for roadway changes have been developed and
evaluated: Alternative A includes actions that are ongoing or programmed
for implementation regardless of what other course of action might be
taken. These include the rehabilitation of the existing road base and
surface and safety improvements such as reflective markings, guardrails,
signing, and skid-resistant surfacing. Alternative B includes the
lengthening of on-ramps and off-ramps and a new third continuous lane
on the outbound roadway between Key Bridge and Spout Run.
Alternative C adds a new third continuous inbound lane between Spout
Run and Key Bridge and a fourth outbound lane through this section.
Alternative D adds third continuous inbound and outbound lanes between
Key and Roosevelt bridges. The alternatives also address possible
improvements to the Lorcom Lane/Spout Run intersection, improvements to
Rosslyn Circle, and various ways to access Rossyln and Key Bridge from
the inbound parkway.
In the public meetings and in written comments to date, the public
expressed general objections to the options of closing or placing vehicular
restrictions on Spout Run Parkway during the morning and evening rush
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hours. The idea of participating in voluntary carpool/vanpool programs
received widespread support. Improved mass transit was requested by
many as an alternative to either mandatory restrictions or expansion of
the parkway's vehicular capacity through a major construction program.
Reaction to options for major parkway construction was mixed. A few
people supported major construction. However, many people expressed
concerns about the loss of parkway scenic and environmental qualities if
major construction was undertaken and felt that if additional lanes were
added, they would attract new users until the parkway segment once
again reached capacity. The year 1990 and 2000 traffic data support
their contention. No alternative would improve more than two of the
eight locations within the study area that are currently "capacity
deficient" (locations where the level of service is E or F or where the
theoretical capacity of the roadway is exceeded). Most of these locations
would remain capacity deficient through the year 2000 regardless of the
amount of parkway improvements or lane additions proposed by the
individual alternatives.
For most segments alternative A would result in the longest travel times.
Alternatives B, C, and D generally would reduce congestion and shorten
travel times compared to alternative A. The potential for accidents would
be reduced over the existing situation in all alternatives, including
alternative A, by improvement of the roadway surface, signing, and
markings. Alternatives B, C, and D would additionally provide for safer
traffic merging throughout the study segment and for safer traffic
weaving on outbound GWMP between Key Bridge and Spout Run. The
primary safety benefits of alternatives B, C, and D would be the likely
reduction of rear-end, run-off-the-road, and side-swipe accidents.
Concerning environmental impacts, alternative A would cause no long-term
negative impacts; however, alternatives B through D would cause
increasingly severe impacts on the parkway's scenic, recreational, and
natural values. Alternative B would result in low to moderate impacts.
Alternatives C and D would involve a considerable increase in the road
surface, extensive cut and fill slopes, and the removal of critical
vegetation along narrow parkway edges. Some impacts could be mitigated
through revegetation, but many others would result in irreparable damage
to the scenic character of this segment of the parkway.
Implementation of any alternative contained in this document will require
coordination among the National Park Service, the Federal Highway
Administration, the Arlington County Department of Public Works, the
District of Columbia Department of Public Works, and the Virginia
Department of Highways and Transportation.
Construction costs for the four alternatives range from $10.3 million for
alternative A up to $31.8 million for alternative D.
Traffic movement, traffic safety, environmental impacts, and project cost
were the primary elements considered in the selection of a preferred
alternative. Alternative B was selected because it would improve traffic
movement and safety at a lower cost and with significantly less adverse
environmental impact than alternatives C or D.
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Summary Comparison of the Effects of the Alternatives
Traffic
conditions
Total number of
capacity-deficient
locations in year
2000
Travel times
Parkway safety
Cost of improve-
ments (1985 dollars)
Alternative B
Alternative A (Preferred Alternative)
resurfacing and basic longer deceleration and
safety improvements acceleration lanes
new continuous lane out-
bound between Key
Bridge and Spout Rup
better travel surface
continued traffic merging
and weaving problems
continued congestion
during peak hours
better travel surface
improvement to traffic
merging problems
some improvement to
traffic weaving outbound
continued congestion
during peak hours
longest travel times
on most segments
shorter travel times than A
inbound on GWMP but longer
than A inbound on Spout
Run
second shortest travel times
outbound
improved due to better same as A plus
surface, signing, and . safer traffic merging
guardrails conditions
moderate potential for
disturbance of archeolo-
gical resources
minor to moderate impact to
historic parkway
additional lanes both in-
bound and outbound be-
ween Spout Run and Key
Bridge
new stacking lane on
inbound GWMP prior to
Roosevelt Bridge
better travel surface
good access to Rosslyn
(and US 50)
improvement to traffic merg-
ing and weaving problems
added congestion at Key
Bridge during morning peak
hours
continued congestion during
peak hours
shorter travel times than B
inbound
Slightly longer travel times
than B outbound
same as A and B plus
more space for traffic
weaving
safer intersection provided
by Lorcom Lane traffic signal
$21,669,000
somewhat higher potential
for disturbance of archeo-
logical resources
major impact to historic
parkway
additional lanes both inbound
and outbound between Spout
Run and Roosevelt Bridge
new ramp from inbound parkway
to Rosslyn Circle
better travel surface
improvement to traffic merg-
merging and weaving problems
added congestion at Key
Bridge during morning peak
hours
continued congestion during
peak hours
shorter travel times than
C inbound
shorter travel times than
B outbound
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Recreational
values
positive impact due to
improved road surface
Overall retention . retention of parkway
of parkway character character
improved safety at the
lowest cost and impact
but continued poor
traffic merging and
continued peak-hour
congestion
Alternative B
(Preferred Alternative)
minor impact due to some
loss of vegetation
positive impact due to
improved road surface
improved Rosslyn Circle
bike trail improvements
improved visitor contact
minor negative impact due to
reduction in vegetative edge
positive impact due to
enhancement of Rosslyn
Circle
minor alteration of parkway
character
improved safety and traffic
merging at moderate cost
and minor impact with
continued peak-hour
congestion
moderate impact due to
disturbance of river edge
and floodplain along out-
bound GWMP
vegetation loss due to
stacking lane
same as B except:
negative impact on Potomac
River Trail caused by four
lanes around piedmont rock
on outbound GWMP
pleasure driving
diminished by loss of scenic
values
major negative impact due to
stacking lane, loss of
vegetative edge, and more
paved surfaces
positive impact due to
enhancement of Rosslyn
Circle
major alteration of parkway
character
improved safety and traffic
merging/weaving at moderate
cost and major impact with
continued peak-hour conges-
tion
moderate to major impact due to
disturbance of river edge and
floodplain along outbound
GWMP
sizable cut and fill slopes
and loss of vegetation
same as B except:
negative impact on Potomac
River Trail caused by four
lanes around piedmont rock
on outbound GWMP
pleasure driving greatly
diminished by loss of scenic
values
Little River shoreline recrea-
tion activity confined to
narrower area
major negative impact due to
loss of vegetative edge, exten-
sive paved surfaces, and cut
and fill slopes and retaining walls
positive impact due to
enhancement of Rosslyn
Circle
severe alteration of parkway
character
improved safety and traffic
merging/weaving at the highest
cost and impact with continued
peak-hour congestion
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CONTENTS
PURPOSE OF AND NEED FOR ACTION 1
PART ONE: ALTERNATIVES INCLUDING
THE PROPOSED ACTION
ALTERNATIVE A 7
ALTERNATIVE B 8
ALTERNATIVE C 13
ALTERNATIVE D 17
OPTIONS CONSIDERED BUT NOT INCLUDED IN THE ALTERNATIVES 21
MITIGATING MEASURES COMMON TO ALL ALTERNATIVES 23
PART TWO: AFFECTED ENVIRONMENT
PARKWAY VALUES 27
Introduction 27
Visual Quality 28
Major Natural Features 29
Climate 31
Air Quality 31
Noise 32
Cultural Resources 34
Recreation Resources 35
Scenic Roadway 35
Cultural and Recreational Sites 35
Trails 37
Adjacent Recreation Resources 38
TRAFFIC ANALYSIS 39
Regional Overview 39
Traffic Origins and Employment Growth 41
Roadway and Operating Characteristics 42
Traffic Volumes 44
Accidents 48
Level of Service 55
Vehicle Occupancy 57
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PART THREE: ENVIRONMENTAL CONSEQUENCES
IMPACTS ON PARKWAY VALUES
Visual Quality 61
Natural Resources
Air Quality 96
Noise 100
Cultural Resources
Recreation 102
TRAFFIC IMPACTS
Introduction 104
Overview 105
Study Area Traffic
Projected Levels of
Accidents 121
Regional Impacts
Flows 109
Service 121
ONSULTATION AND COORDINATION 127
C
Related Studies by Other Agencies 127
Consultation and Coordination in the Preparation of the DEIS
127
Public Involvement 128
Agencies and Organizations to Whom
Have Been Sent 133
Copies of the
DEIS
APPENDIXES
A:
B:
Construction Cost Estimates 135
Methodology Used for the Traffic Impact Analysis
137
140
C:
Consultation with the U.S. Fish and Wildlife Service
GLOSSARY 141
BIBLIOGRAPHY 143
INDEX 147
LIST OF PREPARERS 149
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MAPS
Region X
Existing Conditions 3
Alternative B 11
Alternative C 15
Alternative D 19
TABLES
1. Predicted Existing Carbon Monoxide Concentrations 32
2. FHWA Design Noise Levels 33
3. Predicted Existing Traffic-Generated Noise Levels 33
4. Recreation Sites Served by the Parkway 36
5. Projected Changes in Population, Households, and Employment
from 1980 to 2000 41
6. Current and Historical Weekday Average Daily Traffic on GWMP/
Spout Run Parkway 45
7. Current and Historical Peak-Hour Traffic Volumes on GWMP/
Spout Run Parkway 478. Accident Summary for GWMP/Spout Run Parkway, 1981-1983 49
9. Accident Summary for Rosslyn Circle Area, 1981-1983 51
10. Frequent Accident Locations 53
11. Current Levels of Service 56
12. Vehicle Occupancy, 1981-1982 58
13. Summary of Tree Removals 93
14. Predicted Carbon Monoxide One-Hour Concentrations,
1990 to 2000 97
15. Predicted Carbon Monoxide Eight-Hour Concentrations,
1990 and 2000 98
16. Hydrocarbon Burden Analysis, 1990 and 2000 99
17. Predicted Traffic Noise Impacts, 1990 and 2000 101
18. Summary of Capacity-Deficient Locations 105
19. Short-Term (1990) Projections of Weekday Average Daily Traffic
on GWMP/Spout Run Parkway 110
20. Long-Term (2000) Projections of Weekday Average Daily Traffic on
GWMP/Spout Run Parkway 111
21. Short-Term (1990) Projections of Peak-Hour Traffic on
GWMP/Spout Run Parkway 112
22. Long-Term (2000) Projections of Peak-Hour Traffic on
GWMP/Spout Run, Parkway 113
23. Projected Morning Peak-Hour Levels of Service, 1990 and 2000 122
24. Projected Evening Peak-Hour Levels of Service, 1990 and 2000 123
25. Relative Accident Potentials 125
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Region
George Washington Memorial Parkway
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PURPOSE OF AND NEED FOR THE ACTION
Action is needed to address traffic problems along a 1.6-mile section of
George Washington Memorial Parkway between Theodore Roosevelt Memorial
Bridge (1-66) and Spout Run Parkway; the study area includes the
1.0-mile Spout Run Parkway (from its intersection with GWMP to its
western terminus before Lee Highway) and Rosslyn Circle. The
completion of 1-66 and of the Metropolitan Washington Urban Mass Transit
System (METRO) in Arlington and Fairfax counties, Virginia, was to
significantly reduce transportation use and management problems on GWMP
and Spout Run Parkway. However, continued population growth and
greatly expanded commercial development in these two counties has
prevented the realization of that forecast. Because of its location and
proximity to other regional transportation systems, GWMP not only serves
as a scenic memorial approach to the nation's capital, it also becomes a
congested commuter route during the morning and evening rush hours.
Like most of the highways in the metropolitan area, the study area
roadways now carry traffic volumes that exceed design capacity. The
heavy rush hour traffic, the high traffic speeds during nonpeak periods,
and the condition of the road surface all contribute to a frequent
occurrence of rear-end, sideswipe, and run-off-the-road accidents. The
purpose of the action is to reduce traffic congestion and improve safety
while ensuring the long-term preservation of the parkway's scenic values,
natural and cultural resources, and recreational opportunities.
Within the study area morning congestion begins at the intersection of
Spout Run and Lorcom Lane. Currently, the traffic turning left from
Lorcom Lane onto inbound Spout Run is accommodated by closing the
outbound portion of the Spout Run Parkway and allowing uninterrupted
inbound turns. Where inbound Spout Run merges into inbound GWMP,
long backups occur on both parkways. No exit to Key Bridge and
Rosslyn is allowed during the morning rush hour because neither Rosslyn
Circle, Key Bridge, nor the connecting streets in Georgetown can
accommodate this traffic; backups on GWMP and increased traffic
congestion in Arlington would occur. Traffic headed into the District
must therefore use the Roosevelt Bridge, which is also heavily congested.
This results in substantial traffic backups from the bridge onto the
parkway.
In the evening, high outbound traffic volumes on Roosevelt Bridge create
congestion on the bridge, on the on-ramp to GWMP, and on the outbound
parkway. The congestion is aggravated at the on-ramp from Key Bridge
because of the high volume of outbound vehicles entering the parkway at
this location. Traffic remains highly congested to the Spout Run exit
because of traffic merging and weaving problems.
The traffic congestion on the parkway is part of a more general
transportation network problem that occurs throughout the greater
metropolitan area. Consequently, any proposal to improve traffic flow on
GWMP must be developed in the context of how traffic patterns would
shift throughout the overall network of connecting roadways and streets.
-_ _
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For example, Key and Roosevelt bridges, which link the study area
section of GWMP with city streets in Washington and Rosslyn, also carry
rush-hour traffic volumes that exceed their design capacities, and this
creates traffic backups on the parkway. The roadway intersections at
the east ends of these bridges (M Street at Key Bridge and 23rd Street
and Constitution Avenue at Roosevelt Bridge) are a long-term fixed
constraint on capacity, and the greatest morning traffic congestion occurs
at these intersections.
The heavy traffic volumes carried on GWMP, along with high speeds and
bad weather conditions, are a contributing factor to accidents. Rear-end
collision accidents are the most frequently recorded type within the study
area, and they occur primarily during peak traffic hours. However, all
three fatal accidents during the past three years in the study area
occurred at night.
In addition to traffic congestion and highway safety, GWMP presents
additional concerns that are not generally shared by other regional
roadways. These are the needs to perpetuate the visual qualities that
distinguish it as a parkway, to protect the scenic values of the Potomac
River valley, and to provide recreational and other park experiences for
the local, regional, and national public. Over the years, there has been
an erosion of the pleasurable aspects of parkway use. Increasing
commuter traffic congestion has contributed to this decline. However,
reducing this traffic problem will not reverse the decline unless it is
accomplished in a manner that also protects the parkway's aesthetic and
recreational values.
This document combines planning information from previous Federal
Highway Administration and Arlington County traffic studies and new
information developed by the National Park Service (see the "Consultation
and Coordination" section). It assesses four feasible alternatives to
determine their environmental impacts, focusing on the effects on regional
traffic flow, highway safety, and the visual qualities of the parkway.
Alternative B was selected as the preferred alternative because it would
improve traffic movement and safety at a lower cost and with fewer
adverse environmental impacts than alternatives C or D. However, the
final proposal may be revised based on comments received from the public
and from local, state, and other federal agencies. The proposed action
identified in the final EIS may be a modification of the currently
preferred alternative, another alternative, or a combination of elements
from alternatives B, C, and D, and it may include new elements
suggested during public review.
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Existing Conditions
George Washington Memorial Parkway
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Alternatives including the
Proposed Action
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ALTERNATIVE A
Alternative A is a continuation of existing management. Road base
reconstruction and road resurfacing, which are underway, would be
completed. Additionally, safety improvements, including reflective
markings, guardrails, signing, and placement of skid-resistant surfacing,
would be added. Rosslyn Circle would be improved by removal of the old
bus turnarounds, rehabilitation of the roadway, and new landscaping to
complement the proposed adjacent park above 1-66. A study would be
undertaken to determine what role, if any, the National Park Service
could play in promoting carpool/vanpool use in the area. For example,
existing NPS parking lots, which are heavily used by parkway visitors on
weekends, might also be used for park-and-ride lots during the week.
In summary, the three main components of alternative A are
scheduled road base reconstruction and road resurfacing
safety improvements, such as reflective markings, guardrails,
signing, and skid-resistant surfacing
improvement of Rosslyn Circle
These actions also would be common to alternatives B, C, and D.
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ALTERNATIVE B (PREFERRED ALTERNATIVE)
Alternative B, the preferred alternative, involves structural roadway
changes to improve traffic flow and safety. The merge lane between
inbound Spout Run and GWMP, and all of the existing acceleration and
deceleration lanes, both inbound and outbound, would be lengthened to
allow drivers more space and time to change lanes as they enter and exit
the parkway. In addition, a new continuous lane, approximately 1,300
feet long, would be constructed on outbound GWMP between the on-ramp
from Key Bridge and the Spout Run exit. The new lane would reduce
congestion on that section of the roadway and facilitate traffic weaving
(movement to the right by traffic entering from Key Bridge and movement
to the left by traffic exiting at Spout Run).
The Lorcom Lane/Spout Run intersection would be reconstructed to add a
left turn lane for traffic turning left from inbound Spout Run to Lorcom
Lane. This would allow the obliteration of the turnaround loop on the
inbound Spout Run Parkway. The left turn movement would be
prohibited during the morning rush hours so that traffic turning left onto
Lorcom Lane would not interfere with the heavier traffic turning left from
Lorcom Lane onto inbound Spout Run Parkway. Also, the outbound lanes
on Spout Run would remain closed west of the Lorcom Lane intersection
during the morning rush hours so that through-traffic would not interfere
with the traffic turning left from Lorcom Lane onto inbound Spout Run.
Through-traffic on the inbound portion of Spout Run Parkway would be
restricted to the outside lane through the intersection, leaving the inside
lane open to receive the Lorcom Lane traffic. Inbound traffic would be
funneled into a single lane again just before merging with GWMP traffic.
The longer merge lane, approximately 1,600 feet long, for Spout Run
traffic. merging onto GWMP would allow the removal of the U.S. Park
Police officer from that junction during the morning peak hours.
The GWMP off-ramp to Key Bridge/Rosslyn Circle would be reconstructed
to merge into the 1-66 off-ramp to Lee Highway just before the
intersection with North Lynn Street. Traffic exiting GWMP would thus be
able to turn right onto Key Bridge or continue through the Lee
Highway/Fort Myer Drive intersection. However, the GWMP off-ramp to
Key Bridge/Rosslyn Circle would remain closed during the morning rush
hours to avoid adding traffic to the already congested conditions at
Rosslyn Circle, Key Bridge, and connecting streets, in Georgetown, which
would cause backups onto GWMP.
Rosslyn Circle would be improved as described for alternative A. In
addition, the left-turn lane from North Lynn Street to the on-ramp for
outbound GWMP would be widened and realigned.
The entrance to the Theodore Roosevelt Island parking lot would be
relocated, and a one-way in-and-out traffic flow would be established.
Deceleration and acceleration lanes would be lengthened to improve the
flow of traffic in and out of the parking area.
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In summary, alternative B contains all elements of alternative A plus
Inbound
reconstruction of the Lorcom Lane/Spout Run intersection
obliteration of the inbound turnaround on Spout Run
longer merge lane from Spout Run to GWMP
longer deceleration lanes for GWMP off-ramps to Key and Roosevelt
bridges
reconstruction of the off-ramp to Key Bridge/Rosslyn, adding direct
access to Lee Highway
reconstruction of Rosslyn Circle
Outbound
longer acceleration lane for GWMP on-ramp from Roosevelt Bridge
access improvements at Theodore Roosevelt Island parking lot
new third continuous lane between the on-ramp from Key Bridge and
Spout Run exit
new deceleration lane at the Spout Run turnaround
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ALTERNATIVE C
Alternative C involves additional changes to those ?described for
alternative B. The Spout Run/Lorcom Lane intersection would be
reconstructed to add a third lane for left turns from inbound Spout Run
to Lorcom Lane, as described for alternative B. In addition a traffic
signal would be installed at the intersection, and outbound Spout Run
would no longer be closed west of Lorcom Lane during the morning rush
hour. Inbound Spout Run traffic would be funneled into a single lane
before merging with GWMP traffic, as in alternative B. Unlike alternative
B, which would only lengthen the merge lane, alternative C would add a
new continuous inbound lane, approximately 3,400 feet long, to GWMP
between Spout Run and Key Bridge.
The Rosslyn Circle would be reconstructed as described for alternative B.
The inbound GWMP off-ramp to Key Bridge would also be reconstructed
and opened for use during the morning rush hours. A new stacking lane
approximately 2,600 feet long would replace the existing off-ramp for the
Roosevelt Bridge. The redesigned ramp would be elevated and would exit
GWMP just past Key Bridge, extending into the area between 1-66 and
GWMP. The new off-ramp and stacking lane would free the through-lanes
on inbound GWMP from traffic waiting to get onto Roosevelt Bridge.
Currently, during the morning peak hours, lengthy backups often occur
on GWMP because of traffic congestion on the bridge. Beyond the exit,
the ramp would split into two lanes. The left lane would feed into the
Roosevelt Bridge, and the right lane would merge into outbound US 50,
providing an alternate method of access to the Rosslyn area from that
proposed in alternative B.
Access to the Theodore Roosevelt Island parking lot would be improved,
and the acceleration lane for the GWMP on-ramp from Roosevelt Bridge
would be lengthened, both as in alternative B.
Two new outbound lanes, both about 2,000 feet long, would be added to
the section of GWMP between the Key Bridge on-ramp and the Spout Run
exit. This would further alleviate traffic congestion and reduce the
traffic weaving problem in this segment of the parkway. North of the
Spout Run exit on outbound GWMP, a short (1,000-foot) merge lane would
be added to ease the transition back to two lanes, and the bridge at that
location would be reconstructed to accommodate the merge lane.
On outbound Spout Run, the free-flowing off-ramp from the parkway to
Lorcom Lane would be redesigned to reduce the speed of traffic exiting
Spout Run and thus allow for a safer entrance to the subdivision north of
Spout Run.
In summary, alternative C contains all elements of alternative A plus
Inbound
reconstruction of the Lorcom Lane/Spout Run intersection and
installation of a traffic signal at that intersection
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obliteration of the inbound turnaround on Spout Run
new continuous lane from Spout Run to the off-ramp for Key
Bridge/Rosslyn
reconstruction of the off-ramp to Key Bridge, which would be
reopened for use during morning rush hours
reconstruction of Rosslyn Circle
construction of a new stacking lane to replace the off-ramp to
Roosevelt Bridge and to provide direct access to US 50 into Rosslyn
Outbound
longer acceleration lane for GWMP on-ramp from Roosevelt Bridge
access improvements at Theodore Roosevelt Island parking lot
new third and fourth continuous lanes between the GWMP on-ramp
from Key Bridge and the Spout Run exit
new merge lane north of the Spout Run exit
redesign of the outbound off-ramp from Spout Run Parkway to
Lorcom Lane
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Alternative C
George Washington Memorial Parkway
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ALTERNATIVE D
Alternative D proposes the most structural changes to the parkway
segments. Full third lanes of pavement would be constructed both
inbound and outbound between Spout Run and Roosevelt Bridge. The
total length of the inbound lane would be 5,900 feet, and the outbound
lane would be 6,300 feet. A fourth lane approximately 2,000 feet long
would be added outbound between Key Bridge and Spout Run, as
described for alternative C. Access to the Rosslyn area from inbound
GWMP would be facilitated by a new off-ramp just east (riverside) of the
Marriott Hotel. The Rosslyn Circle would be reconstructed as described
for alternative B. The off-ramp to Key Bridge would be reconstructed
and reopened for use during the morning rush hours, as in alternative
C. Changes to the Spout Run Parkway and the Spout Run/Lorcom Lane
intersection would be the same as described for alternative C.
In summary, alternative D contains all elements of alternative A plus
Inbound
reconstruction of the Lorcom Lane/Spout Run intersection and
installation of a traffic signal at that intersection
obliteration of the inbound turnaround on Spout Run
new third continuous lane from Spout Run to the off-ramp for
Roosevelt Bridge
new off-ramp to the Rosslyn Circle area (right exit)
reconstruction of the off-ramp to Key Bridge, which would be
reopened for use during the morning rush hours
reconstruction of Rosslyn Circle
Outbound
access improvements at Theodore Roosevelt Island parking lot
new third continuous lane between the on-ramp from Roosevelt
Bridge and the Spout Run exit
new fourth continuous lane between the on-ramp from Key Bridge
and the Spout Run exit
new merge lane north of the Spout Run exit
redesign of the outbound off-ramp from Spout Run Parkway to
Lorcom Lane
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Alternative D
George Washington Memorial Parkway
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OPTIONS CONSIDERED BUT NOT INCLUDED IN THE ALTERNATIVES
The following options were considered but rejected during formulation of
the alternatives, for the reasons noted.
HOV-3 restrictions on Spout Run Parkway during the morning and
evening rush hours. Mandatory peak-hour high-occupancy-vehicle
restrictions would be placed on Spout Run traffic. This would divert
low-occupancy Spout Run traffic away from GWMP and reduce the total
peak-hour volumes in the study area without affecting the inbound GWMP
traffic prior to Spout Run. This option was dropped from further
consideration because of the widespread public opposition expressed in
the public meetings, because it would be difficult to enforce, and because
it would restrict cars from Arlington County with less than three persons
desiring to travel on GWMP yet not restrict other parkway users.
HOV-3 restrictions on the off-ramp from GWMP to Key Bridge during the
morning rush hours. The off-ramp from GWMP to Key Bridge would be
reopened for morning rush hour traffic, but HOV restrictions would be
enforced to help control the volume of traffic entering Key Bridge. This
option was dropped from consideration because it would be very difficult
to enforce given the short length of the ramp. Also, any traffic using
the bridge during the morning rush hours would increase the congestion
at Rosslyn Circle, Key Bridge, and connecting streets in Georgetown and
cause backups onto GWMP.
HOV-3 restrictions on the off-ramp from GWMP to Theodore Roosevelt
Bridge during the morning rush hours. This option was dropped from
consideration because it would interrupt existing traffic patterns, channel
additional traffic onto Arlington Memorial Bridge (which is already at
capacity during the morning rush hours), and unreasonably interfere with
general public use of the ramp.
Access to the Rosslyn area through a new tunnel beneath 1-66. A new
exit from inbound GWMP just beyond Key Bridge would lead to a tunnel
beneath all four lanes and the ramps of 1-66, a distance of approximately
600 feet. The tunnel would feed into North Arlington Ridge Road, which
would be changed to a one-way southbound street. A traffic signal would
be installed at the intersection of North Arlington Ridge Road and Wilson
Boulevard. GWMP traffic could either follow Wilson Boulevard into
Rosslyn or continue south on Virginia state route 110. This option was
dropped from consideration because of its cost and impacts on the Rosslyn
area street system.
Elimination of ramp from GWMP to Key Bridge. This option was dropped
because the ramp is needed to properly serve parkway users during the
nonpeak hours. Elimination of the ramp would require people to find
alternate routes to Rosslyn and Georgetown. People traveling to Rosslyn
would be severely inconvenienced.
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Closure of GWMP on-ramp from Key Bridge during afternoon rush hours.
This option was dropped because it would deny parkway access from
Georgetown and Rosslyn during the afternoon peak period, further
overload the Roosevelt Bridge during the afternoon rush period, and
increase use of Lee Highway. (Lee Highway is not now at capacity during
this time period.)
Commuter Fee. Charging a commuter fee for parkway users was rejected
because it would be difficult and costly to administer and enforce and
because it would be complicated by the fact that many parkway users are
visitors to the nation's capital.
Reversible Lanes. The concept of reversible lanes would not be
appropriate for GWMP because of the physical design characteristics of
the parkway and the limited number and design of access points.
Parkway Lighting. A recommendation to place lights along the parkway
was considered incompatible with the aesthetic qualities of the parkway.
However, improved reflective markings should address much of this
concern.
Other Options. Several ideas offered during the preliminary scoping
sessions were beyond the jurisdiction of the National Park Service. They
included an increase in public transportation, the extension of transit
service to the portion of northwest suburban Virginia served by the
parkway, the extension of the Metrorail to Tyson's Corner and Dulles
Airport, further staggering of work hours and closing times, and
restricting or improving various roads and highways under the
jurisdiction of other governmental agencies.
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MITIGATING MEASURES COMMON TO ALL ALTERNATIVES
Regardless of which alternative is implemented, the following measures will
be undertaken to maintain the parkway as a valuable greenbelt and scenic
gateway to Washington, D.C. These actions will be needed especially to
mitigate the adverse effects of alternatives B, C, and D.
Parkway Standards. Specific parkway standards to supplement the
existing NPS road design standards will be developed prior to
construction to ensure that road work is custom-tailored to retain the
parkways' historic distinguishing characteristics and aesthetic appeal.
The standards will include appropriate techniques and materials for
barriers, retaining walls, signs, roadway surfaces, curbing, and drainage
structures.
Comprehensive Planting and Grading Plan. A comprehensive grading and
planting plan will also be completed prior to construction. The grading
plan will specify the action needed to reestablish the natural scene and
original contours to the maximum extent possible and to ensure proper
drainage of all parkway features. The planting plan will specify how the
removal of mature trees, shrubs, and other vegetation will be offset by
replacement with plant materials of suitable type and size to screen
undesired areas and views and to create a pleasing composition.
Rosslyn Circle Comprehensive Design. A comprehensive design will be
prepared for Rosslyn Circle and the connecting bike trail between the
circle and the new bicycle bridge being built over the parkway just
inbound from Key Bridge. The comprehensive design will recognize
Rosslyn Circle as a formal landscaped gateway to the nation's capital.
The design will identify areas where existing pavement will be eliminated,
where the circle will be revegetated, and what planting materials will be
most appropriate. The design will also seek to make the circle area
harmonize with the adjacent Arlington County park over 1-66. The
design will include proposals for a scenic overlook of Georgetown
Waterfront Park and Theodore Roosevelt Island and for enhancement of
the bicycle corridor between Rosslyn Circle and the new bicycle bridge
over the parkway. Recognizing that not all the bicycle route is within
the parkway boundary, the National Park Service will identify
opportunities for coordination with the Virginia Department of Highways
and Transportation. The comprehensive design will be coordinated with a
development concept plan that is currently being prepared for the Little
River shoreline area adjacent to Theodore Roosevelt Island. The
development concept plan addresses bike trail routing to the Arlington
Memorial Bridge area, pedestrian flow, bank fishing, the Theodore
Roosevelt Island parking area, and parkway access.
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Affected Environment
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PARKWAY VALUES
INTRODUCTION
George Washington Memorial Parkway has been recognized worldwide as
one of the finest scenic gateways to a major city. For more than 50
years the parkway has been an integral part of the park system for our
nation's capital, which many believe is the most beautiful in the world.
The national capital park system originated in 1924, when Congress
established the National Capital Park Commission and directed it to
acquire land in the District of Columbia, Maryland, and Virginia suitable
for development into a national capital park, parkway, and playground
system. The broad purpose of the system was "to prevent pollution of
Rock Creek and the Potomac and Anacostia Rivers, [and] to reserve
forests and natural scenery in and about Washington" (PL 292). In 1930
the Capper Crampton Act (46 Stat. 482) called specifically for the
acquisition and establishment of George Washington Memorial Parkway.
The act directed the National Capital Park and Planning Commission (now
known as the National Capital Planning Commission) to construct the
parkway.
The parkway idea is uniquely American. Created by the master park
builders of the 19th century, parkways are publicly respected as one of
the more outstanding amenities of American landscapes. A parkway is not
intended to be just a road. Rather, it is conceived as a linear strip of
parklands encompassing a comprehensive spectrum of environmental and
visual elements and principles, similar to the ingredients used by an
artist to compose a good painting. Parkway designers use terrain, space,
trees, shrubs, rock outcroppings, water features, natural edges, and the
roadway itself as elements of their artistic palettes and combine them in a
highly skilled manner to create expansive pictorial compositions. The full
benefit of the visual variety is gained as the motorist, biker, jogger, or
hiker moves through the arranged sequence of the composition. The
visual experience attracts people to the parkway for the sheer pleasure of
seeing the views from the road.
Landscape architect pioneers Olmstead, Vaux, Cleveland, and Eliot are
credited with the first use of the term parkway. The earliest parkways,
patterned after Eastern Parkway in New York, more nearly resembled
boulevards, being wider and more richly furnished versions of ordinary
streets. In the 1880s and 1890s the term took on an added meaning as
Olmstead, Cleveland, and Eliot applied it to linear parklands, greenbelts,
and other major elements of the landscape used to connect parks and
public facilities in major cities such as Boston. The modern parkway
came into being after World War I as a result of the work of the West-
chester County (New York) Park Commission. The commission, which had
acquired an outstanding technical staff headed by landscape architect
Gilmore D. Clark and civil engineer Jay Downer, initiated a program for
linking their sizable parks with a network of parkways of considerably
improved design. The Bronx River Parkway, the prototype of the
system, established the standards that were followed in the design of
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parkways throughout the country, including GWMP. The elements that
characterize a modern parkway are listed below:
A modern parkway is more than a road. It is a linear park,
dedicated to recreation, that contains a roadway for the movement of
passenger (not commercial) vehicles. It is meant for comfortable
driving in pleasant surroundings, not merely for getting from one
place to another.
Parkway design involves a deliberate attempt to make the roadway
appear like a natural part of the countryside and to eliminate the
perception of parkway boundaries. The road is aligned along gentle
curves, and the lanes may be widely divided on either side of
interesting topographic features. Thus, the parkway strip varies in
width depending upon topographic and cultural conditions.
An abundant use is made of native plant materials. Significant trees
and masses of native vegetation are preserved, and care is taken to
minimize disfiguring scars on hillsides.
Overlooks are provided at scenic points to allow the leisurely viewing
of panoramas or special features.
Views from the parkway are protected from undesirable features by
appropriate buffers.
Access is available only at limited points to minimize the disruptive
effect of merging traffic. Traffic flow through intersections is
facilitated by grade separations. Driving is made considerably safer
and more comfortable by eliminating as many traffic distractions as
possible.
GWMP is part of the legacy left by Olmstead, Eliot, Downer, and Clark.
Eliot and Olmstead identified the Potomac River and its tributaries as
large natural areas that should be conserved as public parklands, and
Eliot played a key role in drafting the Capper-Crampton Act of 1930, the
legislation that established George Washington Memorial Parkway. Downer
and Clark served as consultants to the Bureau of Public Roads during the
development of Mount Vernon Memorial Highway, which was the first
segment of GWMP to be constructed. That segment, which was completed
in 1932 to commemorate the bicentennial of George Washington's birth, was
credited with following the shore of the Potomac without consuming it,
and it is considered one of the East's most attractively sited roadways.
VISUAL QUALITY
As an excellent example of the nation's parkway system, GWMP provides
its travelers with a route through scenic, natural, historic, and
recreational settings. Extending from Mount Vernon on the south to 1-495
on the north, the parkway links presidential memorials, historic sites,
recreation areas that served 9 million people in 1984, and outstanding
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natural features. It protects the natural edges of the Potomac River and
some of its watershed, and it serves as a greenbelt along the Potomac
River valley. Azaleas and dogwoods bloom profusely in the spring, and
in autumn the red maples, oaks, sumacs, and hickories set the hillsides
ablaze with color. White-tailed deer, raccoon, wild turkey, opossum, and
red fox may be seen, and birds abound in the woodlands and wetlands.
Occasional openings afford views over the historic and pastoral C&O Canal
into Georgetown and panoramas of Washington's monumental core.
Downstream from Theodore Roosevelt Island, the river widens
considerably, and distant views spread across the Potomac estuary. In
addition to the scenery enjoyed from the ground, the parkway also
provides a spectacular vista to visitors approaching Washington from the
air.
Through the study area, the parkway's scenic attributes change as it
drops off the Piedmont into the tidewater area at Spout Run. The
vegetative border along the road's edge becomes noticeably narrower, and
the built environments of Georgetown and Rosslyn add starkly contrasting
visual elements to this segment of the parkway. A thin vegetative screen
visually buffers Rosslyn from the parkway at eye level, but Rosslyn's
highrise buildings are visible above the tree line. Also through this
section, the median between the inbound and outbound lanes narrows from
about 100 feet to less than 3 feet at the 1-66 ramps, so oncoming traffic
is much more visible. In spite of the urban encroachment on the parkway
in this area, it retains the vegetative buffer that is essential to its
parkway character and that also protects the views from Theodore
Roosevelt Island.
MAJOR NATURAL FEATURES
The study section of the parkway protects scenic geologic features and a
semblance of natural forest cover isolated between residential and
commercial development and the Potomac River. The Great Falls and the
Potomac River gorge are significant geologic features marking the
transition from the Potomac Palisades of the Piedmont province to the
tidewater regions of the Coastal Plain. Above Great Falls, the Potomac
valley is wide, with steeply sloping sides, and the river is broad,
shallow, and placid. At Great Falls, the character of the river changes.
From there to Theodore Roosevelt Island, the river descends some 90
feet, flowing first through a series of narrow channels between steep
rock cliffs and bedrock islands, then over a stretch of rapids and low
falls. The river meets the tide and becomes an estuary at Little Falls,
still 125 miles from its mouth. Crossing the Coastal Plain, the river
widens, and it is flanked by wide, low terraces and in several places by
bluffs carved into the soft rocks. The fall line (actually a zone)
separating the Piedmont on the northwest from the Coastal Plain on the
southeast passes through the study section of the parkway.
At Key Bridge, the 50-year floodplain is 15.0 feet above mean sea level
and the 100-year floodplain is 17.7 feet above mean sea level. The
average rate of flow in this area is 11,052 cubic feet per second. At the
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Roosevelt Bridge, the 50-year flood would have a volume of 381,000 cfs,
and the 100-year flood, 457,000 cfs. Some segments of GWMP within the
study area are within the 100-year floodplain of the Potomac River, and
most of Spout Run Parkway, both the north and south lanes, is in the
100-year floodplain of Spout Run. Flooding has affected the 100-year
floodplain within the project area at times during the 1930s and 1940s.
Hurricane Agnes in 1973 resulted in a 50-year storm condition. However,
other than spring high-water conditions, no flooding has occurred in the
last 10 years. Spout Run is a flash flood hazard area, and the last major
incident occurred in the mid 1970s.
The Potomac River has good water quality except in areas of localized
pollution, and it is generally suitable for water supply, recreation, and
fishing.
Forests on the higher, well-drained portions of the study area include
oaks and hickories interspersed with beech, red maple, bitternut hickory,
yellow poplar, black walnut, and blackgum. The understory in these
areas consists of dogwoods, holly, laurel, several herbaceous species, and
extensive amounts of poison ivy. Sycamore and ash are the common
canopy trees in the floodplain. The understory there includes eastern
cottonwood, black willow, alder, black birch, blue beech, American elm,
box elder, silver maple, and a diversity of herbaceous plants.
Communities unique to northern Virginia form on rocky slopes and
bedrock terraces. These communities are dominated by oaks that seldom
grow very large. Other trees and shrubs include scrub pine, redcedar,
slippery elm, pignut hickory, hackberry, and several species of
herbaceous plants. The parkway is not known to have any plants
currently listed as endangered or threatened by the U.S. Fish and
Wildlife Service.
At least 35 species of small mammals are found in the parkway. Gray
squirrels are commonly seen; red and gray foxes are occasionally seen;
beaver are notably reestablishing small populations along the Potomac
River; and raccoons and opossums are common nocturnal species. The
varied habitats of the parkway provide cover, food, and water for more
than 175 species of birds. These include several species of birds of prey
that roost and/or nest along the river cliffs or utilize wooded locations
during migration. The woodlands also provide habitat for a wide variety
of tree-nesting songbirds. Numerous species of waterfowl, gulls, and
other shorebirds concentrate along the river, especially during migration
periods. The current status of reptiles and amphibians is not fully
determined, but several reptile and amphibian species seem to be
withstanding the pressures of increasing urbanization. The Potomac
River contains such fish as catfish, carp, sunfish, perch, and bass.
No known endangered or threatened wildlife reside in the parkway, but
bald eagles (Haliaeetus leucocephalus) have been infrequently observed
along the Potomac River. Peregrine falcons (Falco peregrinus) are known
to inhabit the region, but they have not been observed in the parkway.
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CLIMATE
The area has a humid continental climate, with warm and humid summers
and mild winters. Pleasant weather prevails in spring and autumn. The
warmest weather normally occurs in mid July, when average daily high
temperatures are in the upper 80s. The coldest weather normally occurs
in late January and early February, when average low temperatures are
in the upper 20s and average high temperatures are in the middle 40s.
The normal annual precipitation is about 41 inches, usually well
distributed throughout the year. The average annual snowfall is about 20
inches.
AIR QUALITY
The metropolitan Washington region is classified by the U.S.
Environmental Protection Agency as a "nonattainment area" for carbon
monoxide and ozone. This means that the region has not met the national
ambient air quality standards for these pollutants as established by EPA
under the provisions of the Clean Air Act. The Metropolitan Washington
Council of Governments (COG) has prepared a plan outlining how the
region plans to meet the national standards by the year 1987. The
control strategies for mobile sources include the federal motor vehicle
control program, which is expected to reduce emissions of pollutants
directly from the vehicle, augmented by the inspection and maintenance
program in effect in the Washington metropolitan area.
Pollutant-derived ozone is a photochemical oxidant formed from the
reaction of two pollutants--hydrocarbons and nitrogen oxide--in the
presence of sunlight. Of these two precursors to ozone, hydrocarbons
and their effects are more easily measured. Also, controls on
hydrocarbon emissions are more readily available and are generally
considered more effective in reducing ozone. Hydrocarbons are evaluated
on a "mesoscale," or in terms of additional loading for the region as a
whole.
Carbon monoxide has different dispersion characteristics and is a more
localized problem. In the metropolitan Washington region, mobile sources
account for about 94 percent of the total carbon monoxide emissions. The
most severe concentrations are found in the vicinity of heavily congested
signalized intersections. The carbon monoxide one-hour standard is not
being violated in the Washington region, but the eight-hour standard is
being violated (exceeded more than once per year) at certain monitoring
stations near heavily congested signalized intersections. According to the
analysis performed for the COG air quality improvement plan, only one of
the hot spots in northern Virginia exceeded the standard, and this
location was not near the GWMP study area.
There are no air pollution monitoring stations in the vicinity of the GWMP
study area, but the existing air quality was predicted for four sites
where people are likely to stay for extended periods (table 1). The
predicted concentrations include background levels and represent the
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"worst-case" conditions for each site. The most affected site is the
Theodore Roosevelt Island parking area, with a high one-hour
concentration of 4.8 parts per million. However, neither the peak
one-hour concentrations nor the eight-hour concentrations exceed the
national ambient air quality standard for carbon monoxide, which is
35.0 ppm.
Table 1: Predicted Existing Carbon Monoxide Concentrations
One-Hour Concentration (ppm)
Eight-Hour
Concentration (ppm)
Receptors
Morning Peak Hour
Evening Peak Hour
Lorcom Lane
3.6
3.1
2.2
Lee Highway and
3.7
3.5
2.7
Adams Street
Marriott Hotel
3.1
3.4
2.4
Theodore Roosevelt
4.4
4.8
3.3
Island parking lot
Note: The carbon monoxide standard for one hour is 35.0 ppm, and for
the eight-hour averaging period it is 9.0 ppm.
NOISE
Traffic-generated noise and noise from other sources affect overall
environmental quality. The Federal Highway Administration has published
design noise levels, which represent allowable levels of traffic noise on
lands adjacent to highways, for various land use categories (table 2).
The study area falls into category B (parks, residences, motels, etc.),
for which the design noise level is an hourly "equivalent steady state" of
67 decibels.
Existing traffic-generated noise levels were predicted for the study area
using the FHWA traffic noise prediction model (table 3). Predictions were
made for four sites where people are likely to stay for extended periods.
According to the predictions, traffic-generated noise levels are within the
acceptable limits at all four sites. The highest noise level (64.0) occurs
at the parking lot for Theodore Roosevelt Island. This reflects the
proximity of the site to GWMP and the relatively high traffic speeds in
this area. The noise level is almost as high in the residential area near
the intersection of Lee Highway and Adams Street. Noise is less at the
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Table 2: FHWA Design Noise Levels
Category
Design Noise Level
(dBA Leq(h))
A: Lands on which serenity and quiet are 57
of extraordinary significance and serve an (Exterior)
important public need and where the
preservation of those qualities is essential
if the area is to continue to serve its
intended purpose
B: Picnic areas, recreation areas, playgrounds, 67
active sports areas, parks, residences, motels, (Exterior)
hotels, schools, churches, libraries, and
hospitals
C: Developed lands, properties, or activities 72
not included in categories A or B, above (Exterior)
D: Undeveloped lands
E: Residences, motels, hotels, public meeting 52
rooms, schools, churches, libraries, hospitals, (Interior)
and auditoriums
Table 3: Predicted Existing Traffic-Generated Noise Levels
Receptor
Morning Peak Hour
(dBA Leq(h))
Evening Peak Hour
(dBA Leq(h))
Lorcom Lane
51.7
53.4
Lee Highway and Adams Street
63.3
63.6
Marriott Hotel
54.6
53.6
Theodore Roosevelt
Island parking
64.0
62.8
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Marriott Hotel because of the distance it sits back from the roadway, and
less in the residential area along Lorcom Lane because traffic volumes are
lower and because the houses are set back from the street. Throughout
the study area the effects of traffic-generated noise on area residents are
reduced by the vegetative buffer along the parkway. The noise from jet
aircraft following the Potomac River flight path to and from National
Airport overshadows traffic-generated noise in the vicinity of GWMP.
CULTURAL RESOURCES
A large number of sites revealing evidence of Indian occupation from the
Archaic and Woodland periods (circa 8000 B.C. to A.D. 1600) have been
discovered throughout the region surrounding Washington, D.C. No
significant sites have been identified along the study area portion of
GWMP or Spout Run Parkway. However, because of the density of
prehistoric and historic Indian sites in the region, it is probable that
remnants of occupation will be found along the parkway. Algonquian
Indian villages were situated along the Potomac River at the time of the
first recorded European contact by Captain John Smith in 1608. The
Tauxenent Indians occupied the areas now known as Alexandria and
Arlington and Fairfax counties until 1664. One of their small fishing
villages, containing several longhouses, was located on the Virginia shore
in the vicinity of Theodore Roosevelt Island. By the beginning of the
1700s, the local Indians had been forced out of the area by hostile tribes
from the north and encroaching settlement by Europeans from the east
and south. The location of the Tauxenent village has not been
discovered, but it is generally anticipated to be across from Theodore
Roosevelt Island in Virginia, and the features of the village may remain
intact. Other sites might also exist. To protect potential sites, any
actions that will result in ground disturbance along the parkway corridor
will require archeological survey and testing.
Several historic sites are located in and ? immediately adjacent to the
parkway. The historically and architecturally significant Francis Scott
Key Bridge, completed in 1923, crosses the parkway from Rosslyn to
Georgetown. The Key Bridge replaced the Potomac Aqueduct Bridge,
which was built in 1833-43 as a connector for the C&O Canal linking
Georgetown to Alexandria. The abutments of the Aqueduct Bridge still
remain on both sides of the river, and on the Virginia side they are
possibly part of the subbase of the parkway roadway. The Key Bridge
and the Aqueduct Bridge abutments and piers are designated historic
landmarks of Washington, D.C.
Remnants of the entrenchments at Fort Strong, one of the Civil War forts
surrounding Washington, D.C., still exist along Spout Run on the hillside
above the roadway close to 1-66. Also adjacent to the parkway is
Theodore Roosevelt Island National Memorial, which is listed on the
National Register of Historic Places. A variety of remnants of earlier
occupation of the area, such as a quarry site, railroad bridge abutments,
trails, and mill foundations, can be found along GWMP and Spout Run.
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Important cultural values of the parkway also include its landscape
design. The older portion of the parkway, from Memorial Bridge to
Mount Vernon, has been placed on the National Register of Historic Places
for its historic values. Although more recently constructed, the segment
of the parkway in the study area continues the characteristics of the
southern section. Design qualities include alignment of the roadway along
gentle curves with widely divided lanes, use of native plant materials,
and incorporation of natural features in the design of the parkway. An
expanded description of the landscape qualities of the parkway is
provided earlier in this section of the document.
RECREATION RESOURCES
Scenic Roadway
The outstanding beauty of the parkway makes it a popular route for
pleasure driving by both Washington area residents and out-of-town
visitors. A drive along the parkway offers views of the Potomac River
gorge and the prominent memorials and buildings of our nation's capital.
The roadway is beautifully designed and landscaped with ornamental
shrubs and green expanses of lawn bordered by native deciduous
woodlands. The vibrant spring blossoms of azaleas, dogwoods, and
redbuds and the warm fall colors of the woods make spring and autumn
particularly popular seasons for pleasure drives along the parkway.
Many parkway users are through-travelers who prefer the parkway route
because it is the most scenic and relaxing of all the road corridors
leading into Washington from northern Virginia.
Cultural and Recreational Sites
The parkway serves as the major link for a variety of scenic,
recreational, memorial, and historic features in Virginia, Maryland, and
Washington, D.C. The major sites in Virginia and their annual visitation
are noted in table 4. The recreational activities associated with these
sites include picnicking, fishing, jogging, hiking, bicycling, boating,
river viewing, field sports, and nature study. In addition, the National
Park Service and other groups offer organized tours and interpretive
programs at selected sites.
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Table 4: Recreation Sites Served by the Parkway
Site
1984 Visitation
Theodore Roosevelt Island
52,000
United States Marine Corps War Memorial (Iwo Jima)
and Netherlands Carillon
2,500,000
Arlington House
636,000
Lyndon B. Johnson Memorial Grove and
Columbia Island marina
1,000,000
Roaches Run Waterfowl Sanctuary and Gravelly Point
1,300,000
Daingerfield Island and Washington sailing marina
524,000*
Belle Haven
704,000
Fort Hunt
573,000
Riverside picnic area
472,000
Mount Vernon estate
1,100, 000
*Visitation decreased 22 percent from 1983 because of construction
activities.
Theodore Roosevelt Island is the major focus of recreational activity
within the study area. The 88-acre island was added to the national park
system in 1932 and serves both as a presidential memorial and as a
natural park for the "recreation and enjoyment of the public." Three
interpretive trails meander through the island's upland, marsh, and
swamp ecosystems. The memorial occupies 3 acres near the northern end
of the island and includes a 23-foot-high statue of Theodore Roosevelt,
backed by a 30-foot granite panel. Here the life, philosophies, and
contributions of President Theodore Roosevelt are interpreted for the
public.
The island receives about 50,000 visits a year from both out-of-town
tourists and Washington area residents. Most of the visits occur on
weekends; on weekdays, much of the visitation is from school groups.
The National Park Service offers interpretive programs about the island's
natural and archeological history. In addition to attending park
programs, visitors enjoy exploring the island, hiking and jogging its
trails, observing nature, and fishing. Most fishing and picnicking,
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though, occur along the Virginia shoreline, near the parking area, where
the availability of picnic tables, grassy areas, and river vistas provides a
better setting for these activities, and where the proximity of the parking
lot reduces the distance visitors must carry food or equipment. All
visitor facilities, including visitor information, restrooms, and drinking
fountains, are on the island and are inconvenient to those who stay along
the mainland shore. Annual visitation to the shoreline park area is
estimated to be 100,000 visits annually (50,000 who pass through on their
way to the island and 50,000 who stay on the shoreline to fish and
picnic). The parking capacity is often reached on pleasant weekend
days, particularly in the spring and fall, and parking overflows onto the
grassy area next to the paved lot.
Visitation to the Theodore Roosevelt Island area is expected to increase
by 100 to 200 percent once the new bicycle/pedestrian bridge and Mount
Vernon Trail connection are completed (see below). A corresponding
increase in demand for picnicking sites and restrooms is anticipated, and
demand for parking will also likely increase because the area will become
a trailhead for the Mount Vernon Trail.
Trails
The Mount Vernon Trail is a popular scenic and recreational trail that
meanders along the Potomac shoreline parallel to the parkway. The
17-mile trail stretches from Mount Vernon to Arlington Memorial Bridge,
connecting the parkway sites between those points. Over a half million
people are estimated to use the trail every year. Most of the use occurs
on weekends, when Washington area residents come out to enjoy a day's
bicycle excursion and possibly to stop at one or more sites along the
parkway. Hiking, jogging, and fishing are other popular weekend
activities along the trail. During the week, the trail is used by bicycling
commuters and lunchtime joggers. The trail is accessible from several
parking areas along the parkway and from urban centers such as
Alexandria and downtown Washington, D.C. Also, the trail ties into the
Rock Creek and Potomac bicycle route, which begins at Memorial Bridge
and goes 20 miles north along the creek corridor to Lake Needwood,
Maryland. Bicyclists can access the beginning of the C&O Canal towpath
from this route.
The National Park Service plans to extend the Mount Vernon Trail north
from Memorial Bridge to the Theodore Roosevelt Island parking lot by
1986. The trail will tie into the planned Arlington County
pedestrian/bicycle bridge at the north end of the parking area (scheduled
for 1985), thus connecting the Potomac waterfront with the Rosslyn
community, the county bicycle trail system, and the 1-66 bicycle trail.
This connection will open a continuous bicycle route between Mount
Vernon and the Shenandoah Valley by way of the 1-66 trail to the W&OD
Railroad bicycle trail, which passes through Arlington, Fairfax, and
Loudoun counties and terminates in Purcellville, Virginia, just 9 miles
from the Appalachian Trail. The planned pedestrian/bicycle bridge will
provide the only access across the parkway for Arlington County
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residents and Rosslyn workers who want to visit the Potomac waterfront.
In addition, pedestrians and cyclists from the Georgetown community and
the C&O Canal will have access to the new pedestrian/bicycle bridge by
means of Key Bridge.
The Potomac River Trail, an unpaved hiking trail maintained by the
Potomac Appalachian Trail Club, follows the parkway right-of-way for
10.2 miles from the Theodore Roosevelt Island north parking lot to its
terminus at the Capital Beltway. The trail is accessible from the local
Potomac tributary parks and Chain Bridge. Unlike the Mount Vernon
Trail, the Potomac River Trail goes through very rugged, wooded natural
areas and provides excellent opportunities for viewing birds, wildflowers,
waterfalls, cliffs, and riverscapes. Within the study area, where the
strip of land between the river and parkway is narrow, the trail
sometimes comes very close to the parkway. In one section, hikers must
actually walk alongside the roadway and follow trail blazes placed on the
road signs. The National Park Service is studying the feasibility of
making this trail, as well as the Mount Vernon Trail, part of the 700-mile
Potomac Heritage National Scenic Trail.
Adjacent Recreation Resources
GWMP forms the major green space along the eastern edge of Arlington
County. Four county parks and one regional park border GWMP north of
Spout Run Parkway. These are Gulf Branch, Taylor, Donaldson Run,
Windy Run, and Potomac Overlook parks. Combined these parks have 157
acres, two nature centers, and 9 miles of trails used for hiking, jogging,
birding, and nature study. The three tributary parks have trails that
link with the Potomac River Trail.
Downtown Rosslyn currently has three small "vest pocket" parks that are
heavily used by workers during their lunch hours. Each small park may
contain 150 to 200 people at any one time. between 11 a.m. and 3 p.m.
The county plans to develop one more small park in the Rosslyn area.
Also, the state is planning to build a 2-acre park over 1-66 that is
expected to relieve much of the pressure on these other parks. The 1-66
park is slated to be completed by late 1986, at which time the state will
give it to the county to manage. The park will be much larger than the
other parks and will include food concessions, an amphitheater, and water
features. Once the pedestrian/bicycle bridge is completed, a walk to the
Potomac waterfront from Rosslyn parks and offices will be less than a
quarter mile long.
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TRAFFIC ANALYSIS
REGIONAL OVERVIEW
GWMP and Spout Run Parkway are part of a regional highway system that
can be characterized as a network of radial routes focused on Washington,
D.C. The greater Washington metropolitan area is encircled by the
Capital Beltway, which links these radial routes and provides a
circumferential bypass route for through-traffic. The Capital Beltway is
part of the interstate system (1-95/1-495), and it crosses both the north
and south ends of GWMP.
The primary constraint on the highway system in the vicinity of GWMP is
the Potomac River. Seven automobile bridges cross the river in this area
(see the Region map):
Cabin John Bridge (American Legion Bridge) on the Capital Beltway
(1-495), currently three lanes in each direction, but widening to
four lanes is underway
Chain Bridge, two lanes outbound and one lane inbound except
during the morning rush hours, when the center lane reverses
Francis Scott Key Memorial Bridge (US 29), three lanes in each
direction
Theodore Roosevelt Memorial Bridge (1-66 and US 50), three lanes in
each direction
Arlington Memorial Bridge, three lanes in each direction
George Mason Memorial Bridge, Arland D. Williams Memorial Bridge,
and Rochambeau Memorial Bridge (14th Street Bridge), two bridges
consisting of four lanes each to serve traffic in each direction and
an additional bridge of four lanes reserved for HOV-4 vehicles
These bridges all carry heavy traffic loads during rush hours, and an
incident or delay on one has an adverse effect on the other bridges and
on GWMP and the other connecting roads. Another critical factor
affecting traffic flow is the capacity of the road network in the District of
Columbia to absorb the inbound traffic as it crosses the bridges.
The study area of the Spout Run and GWMP roadways is roughly
paralleled by a section of 1-66 that was completed in 1982. On this
portion of 1-66, rush-hour traffic on the inbound lanes during the
morning and on the outbound lanes during the evening is restricted to
HOV-3 vehicles. Trucks are prohibited from using this section of 1-66 at
all times. When this highway opened there was an HOV-4 restriction in
effect between 6:30 and 9:00 a.m. and 3:30 and 6:30 p.m., but the U.S.
Congress subsequently passed legislation to authorize a reduction in the
occupancy requirement to HOV-3 and a reduction in the restricted use
hours to 7:00 to 9:00 a.m. and 4:00 to 6:00 p.m.
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Several other major arterials affect traffic in the vicinity of GWMP. US
50 (Arlington Boulevard) and US 29 (Lee Highway) are heavily used
routes serving the Potomac River crossings. State routes VA 27
(Washington Boulevard) and VA 110 (Jefferson Davis Highway) provide
east-west linkages to the Pentagon and 1-395.
The Washington region is served by extensive Metrobus and Metrorail
systems, both operated by the Washington Metropolitan Area Transit
Authority. The Metrobus system serves all jurisdictions. Most of the
commuter routes in the vicinity of GWMP originate in the northern
Virginia suburbs and terminate at the Rosslyn Metrorail station, but some
cross Key Bridge and terminate in downtown Washington at Farragut
Square. One peak-period bus route from western Fairfax County uses
GWMP.
The Metrorail system, which began operation in 1976, has attracted a
steadily increasing ridership. As of December 31, 1984, 60.5 miles of the
system were in operation, and another 13.4 miles were under
construction. Both the "blue" and "orange" lines serve the Rosslyn
station. The blue line outbound currently terminates at Huntington. The
orange line outbound currently terminates at Ballston in Arlington, but it
will be completed to Vienna in Fairfax County in December 1986. Both
lines connect with all other lines in downtown Washington. An estimated
12,000 passengers boarded the system each weekday at the Rosslyn
station in August 1984.
The Metropolitan Washington Council of Governments periodically conducts
counts of persons and vehicles crossing the Capital Beltway and of those
crossing into the central business district. These counts are undertaken
to monitor trends in transportation pertaining to private vehicle use,
vehicle occupancies, transit use, and truck traffic, and the trends help
determine transportation policy and system requirements. Based on the
beltway count conducted in the fall of 1981 during the morning peak
period (6:30 to 9:30 a.m.), 8 percent of the inbound travelers entered
the larger metropolitan area in a transit vehicle and the remaining 92
percent drove or rode in automobiles. By 1984 transit ridership had
fallen to 6 percent. Transit was more widely used closer to the central
business district than it was in the outlying suburbs; however, the
near-city ridership also decreased between 1981 and 1984. In 1981, 34
percent of the inbound travelers entered the central business district in a
transit vehicle and 66 percent drove or rode in automobiles. In 1983, 31
percent entered the central business district by transit and 69 percent by
automobile. In both 1981 and 1984 approximately 13 percent of those
entering the central business district traveled on the Metrorail system.
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TRAFFIC ORIGINS AND EMPLOYMENT GROWTH
Morning rush-hour traffic on GWMP originates primarily in Fairfax and
Arlington counties, Virginia, and Montgomery County, Maryland. One
morning rush hour count (Bellomo-McGee 1984) indicated that 55 percent
of the traffic was from the outlying suburbs in Virginia (1-495 and VA
123), 24 percent was from the inlying Virginia suburbs (inside the Capital
Beltway), and 21 percent was from Maryland. The main destination of
this commuter traffic is Washington, D.C. While downtown Washington
remains the core employment center within the metro area, the suburban
counties of Arlington, Fairfax, and Montgomery are becoming major
employment centers. The bulk of this employment growth is in the
private sector in the areas of communications, services, and high-tech
industry (table 5). Such growth is expected to be the trend into the
next century. With growing job opportunities in the outlying areas of
Fairfax and Montgomery counties, reverse commuting from Washington and
the inner suburbs is expected to increase. In addition, more business
travel between suburban and downtown offices can be expected since
much work within the private sector is linked to federal government
contracts.
Table 5: Projected Changes in Population, Households,
and Employment from 1980 to 2000
(percent change)
Arlington
County
Fairfax
County
Montgomery
County
Washington,
D.C.
Population
+3
(+12)*
+24
+21
-1
Households
+13
(+24)
+45
+39
+5
Total employment
+35
(+32)
+64
+36
+9
Retail
+18
(+12)
+38
+34
+14
Office
+63
(+45)
+107
+35
+9
Industrial
0
(+2)
+31
+46
+10
Other
-6
(-38)
+16
+31
+11
Source: Metropolitan Washington Council of Governments, Round I I I
Intermediate Forecasts for 1980 and 2000.
*Numbers in parentheses denote the projected changes for the Rosslyn/
Spout Run area. These percentages were derived primarily from COG
forecasts and Arlington County development plans.
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Growth in Fairfax County will occur in and around Tysons Corner,
Reston, Fair Oaks, and the US 50/1-66 intersection. As these employment
centers develop, the county's major population growth is expected to
occur in western Fairfax County, specifically Herndon, Reston, Chantilly,
Centreville, and West Springfield. These locations are within reasonable
commuting distance of the new suburban job centers, have a supply of
vacant land, and are comparatively less expensive. No substantial
increase in population is projected for those Fairfax County areas closer
to Washington, such as Falls Church, McLean, or Vienna. The only
exception is the area bordering Alexandria near the Metrorail system.
In Montgomery County the growth in employment will continue primarily
along the 1-270 and US 29 corridors. This growth will be spurred by the
increasing attractiveness of the Washington/Baltimore area as an
investment market. Also, the county has developed a good base of
high-tech industries and is expecting to attract even more. As this
growth occurs, more and more commuting will occur from Maryland
counties outside the metro area. The most significant population growth
in the county is expected in the outlying areas of the 1-270 and US 29
corridors, where plenty of vacant land is available. Population in inner
areas such as Silver Spring, Wheaton, and Bethesda is expected to
decline or rise only slightly.
The proximity of Arlington to downtown Washington, National Airport, and
the Metrorail system is making the county an increasingly popular location
for businesses, especially offices and hotels. Available office space (both
old and new) is rapidly being leased, and the vacancy rate currently is
only 2 percent. The demand for office space is spurring a high level of
new construction and redevelopment in the Metrorail corridors. The
long-range impact of this construction growth will be a dramatic increase
in office employment levels, with an echoing increase in retail activities
and household numbers.
ROADWAY AND OPERATING CHARACTERISTICS
The northern portion of the GWMP study area is situated along a narrow
escarpment that slopes steeply toward the river. The inbound and
outbound roadways are separated by a vertical distance of about 93.5 feet
at the steepest point north of Key Bridge. The inbound roadbed grade
is about 7 percent through this steepest section. It gradually flattens to
a level grade in the vicinity of Key Bridge. The two roadways remain
separated, however, by a slope of approximately 11.5 feet. The road
generally follows the contours of the Potomac River within the study area.
There are slight S-curves in both the inbound and the outbound
roadways north of Key Bridge and a sharper curve between Key Bridge
and Theodore Roosevelt Island.
The Spout Run Parkway follows the gentle curves of the Spout Run
streambed, descending about 100 feet to its intersection with GWMP. The
inbound and outbound roadways, which lie on either side of the
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streambed, are separated by a vertical distance of about 40 feet at one
steep point.
Both parkways have two 12-foot lanes in each direction. In areas where
the inbound and outbound lanes are not separated by steep grades, they
are separated by median dividers. On GWMP the medians range in width
from 6 feet to about 240 feet. There are no paved shoulders on either
parkway. Disabled vehicles can drive over the 3-inch-high mountable
curbs to grassy areas on either side of the roadway.
A major exception to the two-lane configuration occurs near the
intersection of inbound GWMP and Spout Run. Beginning about 800 feet
from the intersection on GWMP and 730 feet on Spout Run, traffic on each
roadway is funneled by roadway striping into a single lane that continues
through the merge area to re-form GWMP's two-lane roadway. Traffic at
this intersection is managed differently during the morning rush hours,
as described below.
Both parkways are limited-access roadways. Within the study area GWMP
can be accessed only from Spout Run Parkway (inbound only), Key
Bridge (outbound only), and Roosevelt Bridge (outbound only). Exits
off GWMP are similarly limited and exist only at Spout Run (outbound
only), Key Bridge (inbound only), and Roosevelt Bridge (inbound only).
The only entrance and exit for the parking lot for Theodore Roosevelt
Island is from the outbound lanes of GWMP. Drivers wishing to leave the
parking lot and return to Washington, D.C., or points south must use
the Spout Run turnaround.
Spout Run Parkway is accessible from Lee Highway via Kirkwood Road or
from Lorcom Lane inbound, and from GWMP outbound. Turnarounds are
provided for traffic in both directions. The outbound turnaround
accommodates outbound GWMP traffic desiring to go into Washington, D.C.
Since there is no exit from outbound GWMP to the Roosevelt Bridge or
Key Bridge, outbound travelers must turn around on Spout Run and
approach the bridges from inbound GWMP. The inbound turnaround
accommodates inbound Spout Run traffic desiring to turn onto Lorcom
Lane, since left turns onto Lorcom Lane are currently prohibited at all
times.
The posted speed limit on GWMP and the Spout Run Parkway within the
study area is 40 mph. During the rush hours the actual speeds slow to
about 25 mph inbound between Spout Run and Key Bridge in the morning
and to about 20 mph outbound between Key Bridge and Spout Run in the
afternoon. At night and early in the morning, a high percentage of
vehcles travel faster than 50 mph.
During the morning peak period (7:00 to 9:00 a.m.) traffic controls are
imposed at three locations.
GWMP/Spout Run intersection: At all other times the inbound traffic
on each parkway is funneled into a single lane before reaching the
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merge area. During the morning peak period, however, two lanes of
traffic are permitted on both roadways. (Signs advising of this
condition are manually operated by U.S. Park Police personnel.) A
U.S. Park Police officer directs traffic through the intersection,
allowing two lanes of traffic to proceed from one parkway while
stopping the two lanes of traffic on the other. About 6 minutes is
allowed for GWMP traffic, then 2 minutes for Spout Run Parkway
traffic. Queues form on both parkways, often as far as 2 miles on
GWMP prior to the Spout Run Parkway entrance.
Off-ramp to Key Bridge: A physical barrier is placed across the
GWMP off-ramp to Key Bridge from 7:00 a.m. to 9:00 a.m.
Frequently a queue develops prior to 9:00 a.m. from vehicles in the
deceleration lane waiting for the barricades to be removed, despite
the No Waiting" signs.
Spout Run/Lorcom Lane intersection: Traffic is controlled to allow
uninterrupted left turns from Lorcom Lane to inbound Spout Run
during the morning rush hours. U.S. Park Police place barricades
on outbound Spout Run Parkway east of the intersection to divert
outbound through-traffic to Lorcom Lane and keep it from interfering
with left turns onto inbound Spout Run.
TRAFFIC VOLUMES
Three measures have been used to evaluate vehicle travel patterns and
trends in the study area: weekday average daily traffic (ADT), weekday
morning peak-hour volume, and weekday evening peak-hour volume.
As of this report date, no continuous traffic counting programs have been
implemented for either parkway. However, volume data have been
collected periodically on selected segments in the study area by various
agencies, including the Eastern Direct Federal Division of the Federal
Highway Administration (at the request of the National Park Service), the
Virginia Department of Highways and Transportation, the Arlington
County Department of Public Works, and the District of Columbia
Department of Public Works.
The available traffic volume data include 24-hour, 48-hour, and 72-hour
counts, and 9-day to 15-day counts collected periodically between June
1982 and August 1984. The data obtained by FHWA formed the basis for
the derived weekday ADT and the morning peak-hour volumes. FHWA
collected multiple-day traffic counts using automatic data collection
equipment during September and October 1982, January and February
1983, February and March 1984, and June and July 1984.
The weekday ADT for sections of GWMP and Spout Run are shown on
table 6. This table shows the most recent traffic counts (June and July
1984) and historical counts to illustrate the changes in traffic volumes
over time. As shown on table 6, the weekday ADT increased between
1972 and September 1982. After the opening of 1-66 inside the beltway in
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Table 6: Current and Historical Weekday Average Daily Traffic
on GWMP/Spout Run Parkway
Weekday Average Daily Traffic (vehicles per day)
Route Segment
1972
1977
Sept.
1982
Feb.
1983*
Feb.
1984**
July
1984
Inbound
GWMP from VA 123 to
Spout Run
25,000
30,000
30,000
25,500
22,500
26,500
GWMP from Spout Run
to off-ramp to Key
Bridge/Rosslyn
34,000
39,000
40,000
35,000
30,000
35,000
GWMP from off-ramp to
Key Bridge/Rosslyn to off-
ramp to Roosevelt Bridge
26,000
28,000
29,000
27,500
23,500
27,500
GWMP from off-ramp to
Roosevelt Bridge to on-
ramp from US 50
17,000
18,000
16,500
18,000
18,000
20,000
Off-ramp to Key Bridge/
Rosslyn
8,000
11,000
11,000
7,500
6,500
7,500
Off-ramp to Roosevelt
Bridge
9,000
10,000
12,500
9,500
5,500
7,500
Spout Run Parkway
9,000
9,000
10,000
9,500
7,500
8,500
Outbound
GWMP from on-ramp from
Memorial Circle to on-ramp
from Roosevelt Bridge
20,000
21,000
22,000
19,000
18,500
20,000
GWMP from on-ramp from
Roosevelt Bridge to on-ramp
from Key Bridge/Rosslyn
26,000
27,000
32,000
26,000
26,000
28,000
GWMP from on-ramp from
Key Bridge/Rosslyn to
Spout Run
36,000
37,000
49,000
38,000
37,000
42,000
GWMP from Spout Run
to VA 123
25,000
27,500
37,500
28,500
27,500
30,500
On-ramp from Roosevelt
Bridge
6,000
6,000
10,000
7,000
7,500
8,000
On-ramp from Key
Bridge/Rosslyn
13,000
10,000
17,000
12,000
11,000
14,000
Spout Run Parkway
11,000
9,500
11,500
9,500
9,500
11,500
Source: Derived from data collected by FHWA and rounded to the nearest
500 vehicles per day.
*I-66 opened at HOV-4.
**I-66 changed to HOV-3.
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December 1982, the traffic patterns changed. A comparison of the data
for September 1982 and February 1983 shows that significant reductions in
traffic occurred throughout the GWMP study area, and most notably on
the on-ramps from Key and Roosevelt bridges, the critical outbound
section of GWMP between Key Bridge and Spout Run, and the off-ramps
to both Key and Roosevelt bridges. Traffic flows normally fluctuate
seasonally, so there may be differences between September/October traffic
counts and January/February traffic counts attributable to factors other
than the opening of 1-66, such as recreational travel or weather.
However, it was concluded that the changes in traffic patterns
represented by the data are mostly attributable to the opening of 1-66.
Another change in traffic patterns occurred in January 1984 when the
HOV restrictions on 1-66 were changed from HOV-4 to HOV-3. This did
not significantly change the ADT volumes on outbound GWMP, but it
resulted in further reductions in ADT on inbound GWMP. The most
recent traffic counts, collected in June and July of 1984, reflect
subsequent increases in weekday ADT throughout the GWMP study area.
In fact, traffic in the summer of 1984 was once again as high or higher
than the comparable traffic in the winter of 1983.
GWMP carries heavy traffic during the peak hours (see table 7). In the
most critical segment the evening peak-hour volumes on outbound GWMP
between the on-ramp from Key Bridge/Rosslyn and the Spout Run
Parkway regularly exceed the theoretical capacity of the roadway.
Theoretical capacity, as defined in the Highway Capacity Manual (National
Academy of Sciences 1965), is 2,000 vehicles per hour per lane under
ideal uninterrupted conditions.
The opening of 1-66 had little effect on morning peak-hour traffic.
However, a decrease in evening peak-hour traffic occurred on outbound
GWMP between Memorial Circle and Key Bridge after the opening of 1-66.
After the reduction in the high-occupancy-vehicle requirements on 1-66
from HOV-4 to HOV-3 in January 1984, the morning peak-hour traffic also
decreased significantly. Recent traffic counts collected in June and July
of 1984 show only slight recent changes in the morning and evening
peak-hour volumes.
A critical section of the GWMP study area is the merge and weaving
section on the outbound roadway between Key Bridge and Spout Run. As
many as 4,500 vehicles travel this section in the evening peak hour.
This is 500 vehicles more than the theoretical capacity of this two-lane
roadway. The vehicles entering this section of GWMP from the on-ramp
from Key Bridge/Rosslyn must merge into the left lane of GWMP. Traffic
congestion on GWMP is aggravated by these vehicles merging onto the
main section of the roadway, and the congested conditions on GWMP cause
considerable queuing on the on-ramp from Key Bridge/Rosslyn. A license
plate survey was conducted to analyze the evening rush hour weaving
patterns in this short (0.3-mile) section of GWMP. The survey indicated
that approximately 23 percent of the vehicles entering from the on-ramp
from Key Bridge/Rosslyn exit at Spout Run Parkway. This amounts to
about 300 vehicles during the evening peak hour. Approximately 51
percent of the vehicles traveling in the left lane of GWMP just before the
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Table 7: Current and Historical Peak-Hour Traffic Volumes
on GWMP/Spout Run Parkway
Route Segment
1972
1977
Sept.
1982
Feb.
1983*
Feb.
1984**
July
1984
Inbound/Morning Peak Hour
GWMP from VA 123 to
Spout Run
2,400
2,750
3,000
3,000
2,600
2,750
GWMP from Spout Run
to off-ramp to Key
Bridge/Rosslyn
3,900
3,900
3,700
3,800
3,300
3,450
GWMP from off-ramp to
Key Bridge/Rosslyn to off-
ramp to Roosevelt Bridge
3,900
3,900
3,700
3,800
3,300
3,450
GWMP from off-ramp to
Roosevelt Bridge to on-
ramp from US 50
2,300
2,300
1,400
1,700
2,200
2,150
Off-ramp to Key Bridge/
Rosslyn***
0
0
0
0
0
0
Off-ramp to Roosevelt
Bridge
1,600
1,600
2,050
2,100
1,100
1,300
Spout Run Parkway
1,500
1,150
700
800
700
700
Outbound/Evening Peak Hour
GWMP from on-ramp from
Memorial Circle to on-ramp
from Roosevelt Bridge 2,200
2,200
2,750
2,100
2,050
1,900
GWMP from on-ramp from
Roosevelt Bridge to on-ramp
from Key Bridge/Rosslyn 2,900
2,900
3,850
3,250
3,200
3,000
GWMP from on-ramp from
Key Bridge/Rosslyn to
Spout Run 4,200
4,500
4,350
4,400
4,350
4,350
GWMP from Spout Run
to VA 123 3,000
3,500
3,300
3,350
3,200
3,250
On-ramp from Roosevelt
Bridge 700
700
1,150
1,200
1,150
1,100
On-ramp from Key
Bridge/Rosslyn 1 , 300
1,600
1,400
1 , 300
1,350
1,600
Spout Run Parkway 1,200
1,000
1,000
1,050
1,150
1,100
Source: Derived from raw traffic count data collected by FHWA and rounded
to the nearest 50 vehicles per hour.
*I-66 opened at HOV-4.
**I-66 changed to HOV-3.
***Closed to traffic from 7:00 to 9:00 a.m.
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ramp from Key Bridge/Rosslyn also exit at Spout Run Parkway. This
amounts to almost 800 vehicles during the evening peak hour. In all, as
many as 550 vehicles change lanes in this 0.3-mile-long, two-lane section
of GWMP. An average of 21 percent of the traffic on outbound GWMP
before the Key Bridge ramp had Maryland license plates, compared to an
average of 25 percent of the traffic beyond the Spout Run exit.
ACCIDENTS
Based on a 1984 traffic engineering and safety improvement study for all
of GWMP north of Alexandria, the accident rate per million vehicle miles
of travel was 1.83 from 1981 through 1983. This accident rate was
between the average rate for all Virginia four-lane primary highways with
fully controlled access (0.9) and the average rate for all Virginia
four-lane primary highways with partially controlled access (2.3), as
indicated by 1981 and 1982 accident data from the Virginia Department of
Highways and Transportation. It should be noted that the National Park
Service records all accidents, whereas the commonwealth of Virginia
records those accidents that exceed $500 in property damage.
There were 420 reported accidents in the study area between January 1,
1981, and December 31, 1983, based on accident data obtained from the
Arlington County Department of Public Works and the U.S. Park Police.
Of this total, 123 accidents occurred in the Rosslyn Circle area and the
remaining 297 occurred on GWMP, the on- and off-ramps, and Spout Run
Parkway (see tables 8 and 9). The accidents caused three fatalities and
101 injuries between 1981 and 1983. All of the fatalities occurred at
night.
Approximately 43 percent of the accidents that occurred in 1981-83 in the
study area were rear-end collisions, 17 percent were side-swipe collisions
between vehicles traveling in the same direction, and almost 15 percent
were right-angle collisions. These percentages indicate a significant
safety problem related to congestion, and this finding is reinforced by
the relatively high incidence of accidents during the rush hours compared
to the proportion of total traffic that occurs during these periods.
Approximately 33 percent of all the reported accidents on inbound GWMP
occurred during the weekday morning peak period (6:00-10:00 a.m.).
This was a relatively high percentage considering that only 25 percent of
the average annual vehicle miles of travel occurred during that time
period. Similarly, more than 29 percent of all reported accidents on
outbound GWMP occurred during the weekday evening peak period
(3:00-7:00 p.m.), while only 25 percent of the average annual vehicle
miles of travel occurred during those hours.
Seventy-five percent of the 420 accidents reported in the study area
occurred at ten specific locations. These locations are listed in table 10.
At the signalized intersection of Fort Myer Drive and the on-ramp to
outbound GWMP, 57 accidents were reported between 1981 and 1983.
Almost half of these occurred between the hours of 11:30 p.m. and
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Table 8: Accident Summary for GWMP/Spout Run Parkway,
1981-1983
Accidents
Average
Property
Accident
Personal
Damage
Rate
Route Segment
Fatalities
Injuries
Fatal
Injury
Only
Total
(No./MVM*)
Inbound
Spout Run Parkway
from Lorcom Lane
to turnaround
--
1
--
1
3
4
6.4
Spout Run Parkway
from turnaround to
junction with GWMP
--
15
--
5
2
7
1.2
GWMP from north
end of bridge over
Spout Run to junction
with Spout Run
Parkway
--
3
--
3
20
23
7.5
GWMP from Spout
Run Parkway to off-
ramp to Key Bridge/
Rosslyn
--
9
--
8
44
52
2.0
Off-ramp from GWMP
to Key Bridge/
Rosslyn
--
4
--
4
18
22
12.1
GWMP from off-ramp
to Key Bridge/
Rosslyn to off-ramp
to Roosevelt Bridge
--
7
--
5
13
18
1.3
Off-ramp from GWMP
to Roosevelt Bridge
--
GWMP from off-ramp
to Roosevelt Bridge
to US 50 overpass
--
1
--
1
6
7
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Accidents
Average
Property
Accident
Personal
Damage
Rate
Route Segment
Fatalities
Injuries
Fatal
Injury
Only
Total
(No./MVM*)
Outbound
GWMP from south
end of Boundary
Channel Bridge to
on-ramp from
Roosevelt Bridge
On-ramp from
Roosevelt Bridge
to GWMP
GWMP from on-ramp
from Roosevelt
Bridge to access to
Roosevelt Island
parking area
1
3
1
2
8
11
2.3
GWMP from access to
Roosevelt Island
parking area to on-
ramp from Key
Bridge/Rosslyn
On-ramp from Key
Bridge/Rosslyn to
GWMP
3
--
2
10
12
1.9
GWMP from on-ramp
from Key Bridge/
Rosslyn to Spout
Run
2
--
S
20
22
1.5
GWMP from Spout
Run exit to north
end of bridge
over Spout Run
--
--
11
11
5.1
Spout Run Parkway
from junction with
GWMP to turnaround
2
7
1
6
8
15
2.0
Spout Run Parkway
from turnaround to
Lorcom Lane
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Table 9: Accident Summary for Rosslyn Circle Area,
1981-1983
Accidents
Average
Property
Accident
Personal
Damage
Rate
Route Segment
Fatalities
Injuries
Fatal
Injury
Only
Total
(No./MVM*)
Westbound Fort
Myer Drive from end
of Key Bridge to on-
ramp to GWMP
--
8
--
5
48
53
42.7
Westbound Fort
Myer Drive from on-
ramp to GWMP to Lee
Highway intersection
--
4
--
3
12
15
5.8
Eastbound Lynn
Street from Lee
Highway intersection
to on-ramp to
GWMP
--
6
--
6
38
44
20.6
Crossover from east-
bound Lynn Street
to on-ramp to
GWMP
--
1
--
1
3
4
15.6
Eastbound Lynn
Street from off-ramp
from GWMP to Key
Bridge
7
7
6.0
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4:00 a.m. Alcohol was a major contributing factor to these accidents. In
fact, in 50 percent of these late-night accidents, at least one of the
drivers involved was cited by the investigating officer on the report as
being under the influence of alcohol. The most common.type of accident
was a rear-end collision in which the first vehicle traveling across Key
Bridge slowed or stopped for a red light and was struck in the rear by
the second vehicle. More than 72 percent of the reported accidents at
this location were rear-end collisions.
At the intersection of North Lynn Street and the off-ramp from inbound
GWMP, 50 accidents were reported between 1981 and 1983. About 36
percent occurred during the evening peak period (3:00-7:00 p.m.) when
traffic on North Lynn Street was heavy and the ramp from inbound GWMP
was open. Half of all the accidents were right-angle collisions in which a
vehicle leaving the off-ramp was struck by a vehicle proceeding toward
Key Bridge on North Lynn Street. Another 20 percent were side-swipe
collisions involving one vehicle desiring to cross North Lynn Street to
make a left turn to Fort Myer Drive and another vehicle attempting to go
straight on North Lynn Street.
At the intersection of Lorcom Lane and Spout Run Parkway, 37 accidents
were reported between 1981 and 1983. More than three-quarters of these
accidents were right-angle collisions involving one vehicle pulling out from
the Lorcom Lane approach and another vehicle proceeding toward Lee
Highway on Spout Run Parkway. Additional accidents of this type would
have been expected if outbound Spout Run had not been closed to
through-traffic west of Lorcom Lane during the morning rush hours.
At the junction of inbound GWMP and the off-ramp to Key Bridge/
Rosslyn, 32 accidents were reported between 1981 and 1983. More than
half of the accidents were rear-end collisions involving two vehicles on
GWMP, and another 34 percent were accidents in which a vehicle ran off
the right side of the road and hit a sign post, guardrail, or pole. The
curve at this location is extremely sharp and sight-distance for drivers
on GWMP is severely restricted by the Key Bridge abutments.
Twenty-two percent of the reported accidents at this location occurred
between 7:00 a.m. and 10:00 a.m. As described previously, the ramp to
Key Bridge is currently closed during the morning peak period (7:00 to
9:00 a. m. ). However, cars often illegally queue up at this location
before 9:00 a.m., waiting for the ramp to open.
At the junction of outbound GWMP and the ramp from Roosevelt Bridge,
22 accidents were reported between 1981 and 1983. More than 59 percent
of the accidents were rear-end collisions involving two or more vehicles
on the ramp. Approximately 27 percent of all accidents occurred between
3:00 and 7:00 p.m. on weekdays, and another 27 percent occurred
between 7:00 and 9:30 p.m. on weekdays. Sight distance to the merge
area for outbound drivers on GWMP is severely restricted by the ramp
structure and the vertical alignment. Sight distance is also very limited
for drivers entering the parkway from the ramp; near the end of the
ramp, these drivers have to look back to observe vehicles approaching on
GWMP. The acceleration lane is too short for operating conditions,
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Table 10: Frequent Accident Locations
Average Annual
Accident Frequency Average
1981-1983 Accident Rate
Inbound
Inbound Lorcom Lane and Spout Run
Parkway (including the outbound
Spout Run Parkway approach
to the intersection) 12 1.0/MVE
Spout Run Parkway and inbound
GWMP 7 0.5/MV E
GWMP between Spout Run Parkway
and off-ramp to Key Bridge/Rosslyn 13* 5.1/MVM**
Junction of GWMP and off-ramp
to Key Bridge/Rosslyn 11 0.8/MVE
Off-ramp to Key Bridge/Rosslyn
3* 12.1/MVM
Key Bridge off-ramp at Lynn Street 17 1.0/MVE
Outbound
On-ramp from Roosevelt Bridge 7 0.7/MVE
On-ramp from Key Bridge/Rosslyn at
Fort Myer Drive 19 1 .1 /MV E***
GWMP at on-ramp from Key Bridge/
Rosslyn 10 0.6/MVE
Spout Run Parkway 5* 2.0/MVM
Total 104
* These are nonintersection accidents. Accidents that occurred at the
intersections at the ends of this roadway section are not included.
** MVM = million vehicle miles
***MVE = million vehicles entering
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especially during the evening peak period, when traffic on the ramp is
heavy. Field observations confirm that drivers on GWMP approaching the
junction often swerve erratically into the left lane to avoid vehicles
entering the traffic stream from the ramp.
At the junction of the on-ramp from Key Bridge/Rosslyn and outbound
GWMP, 30 accidents were reported between 1981 and 1983. More than 53
percent of these were rear-end collisions involving two or more vehicles
on outbound GWMP, 20 percent were rear-end collisions involving two or
more vehicles on the ramp, and 20 percent were side-swipe collisions
involving one vehicle traveling on GWMP and another vehicle entering
GWMP from the ramp. More than 43 percent of all the reported accidents
occurred during the weekday evening peak period (3:00 to 7:00 p.m.).
Another 30 percent occurred during the weekend, when traffic volumes
were lower but speeds were higher.
At the junction of inbound GWMP and inbound Spout Run Parkway, 22
accidents were reported between 1981 and 1983. All but one of the
accidents were rear-end collisions involving two vehicles on GWMP.
Sixty-eight percent of these accidents occurred during the weekday
morning peak period (6:00 to 10:00 a.m.), and 36 percent occurred
between 7:00 and 9:00 a.m. As was stated earlier, between approximately
7:00 and 9:00 a.m., a U.S. Park Police officer directs traffic at this
intersection. During this time period, inbound traffic on GWMP does not
have the continuous right-of-way and must sometimes stop at this
junction. This stop-and-go traffic condition is conducive to rear-end
collisions.
At inbound GWMP between inbound Spout Run Parkway and the off-ramp
to Key Bridge/Rosslyn, 38 accidents were reported between 1981 and
1983, 'not including the accidents that occurred at the junctions at either
end of this segment. Almost 37 percent of these accidents occurred
during the weekday morning peak period (6:00 to 10:00 a.m.).
Fifty-eight percent of the total reported accidents were rear-end
collisions, and an additional 18 percent were accidents in which a vehicle
ran off the road and hit a tree, stone wall, post, or bridge abutment.
At outbound Spout Run Parkway from the junction with outbound GWMP to
the turnaround, 15 accidents were reported between 1981 and 1983. In
more than half of the reported accidents, a vehicle ran off the road.
One of these accidents resulted in two fatalities, and five other accidents
resulted in a total of seven personal injuries. This roadway section had
the highest injury rate of all the locations examined in the study area
(see table 10). The alignment of this section of Spout Run Parkway is
along an upgrade and is curvilinear.
At the off-ramp from inbound GWMP to Key Bridge/Rosslyn, 10 accidents
were reported between 1981 and 1983, not including the accidents that
occurred at the junctions at either end of this segment. The curvature
of the ramp is very sharp; it has less than a 100-foot radius at the apex,
an 8 percent grade on one short segment, and a 5 percent grade overall.
Interestingly, 60 percent of the reported accidents occurred during the
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weekend. (This ramp is currently closed during the weekday morning
peak period, when a large proportion of accidents would otherwise be
expected to occur.)
LEVEL OF SERVICE
A key determinant of the ability of a road system to accommodate the
travel demand is the level of service concept. Level of service is a
qualitative assessment of vehicle mobility along a roadway or through an
intersection and is represented by a rating between A and F, with A
representing little or no delay and F representing extreme congestion.
The six levels of service are defined as follows:
A: Free flow conditions, no delays, and all signal phases of
sufficient duration to clear all approaching vehicles
B: Stable flow conditions, little delay, some signal phases unable
to handle all approaching vehicles
C: Stable flow conditions, low to moderate delays, full use of peak
directional signal phase(s)
D: Approaching unstable flow conditions, moderate to heavy
delays, significant signal-time deficiencies for short durations
during the peak period
E: Unstable flow conditions, significant delays, significant
signal-time deficiencies throughout the peak period
F: Forced flow conditions, low travel speeds, demand volumes well
above capacity (This condition is reached when vehicles
released by an upstream signal are unable to proceed because
of backups from a downstream signal.)
Levels of service were computed using the procedures outlined in Interim
Materials on Highway Capacity. This report was released by the
Transportation Research Board as an interim report to be distributed
prior to the publication of a new highway capacity manual in the
mid 1980s. The "critical movement analysis procedure" was employed to
assess the level of service at ten locations in the study area. The
results of this assessment are listed in table 11. As shown on the table,
many locations have very low levels of service during the peak periods.
During the morning peak hour, level of service is E or F at the following
locations:
junction of Spout Run Parkway and inbound GWMP
inbound GWMP off-ramp to Roosevelt Bridge
junction of inbound 1-66 and the GWMP off-ramp to Roosevelt Bridge
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Intersection of Lorcom Lane and Spout Run Parkway
Traffic turning left from Lorcom Lane onto Spout
Run Parkway
Junction of inbound GWMP and Spout Run Parkway
All traffic entering intersection
Junction of inbound GWMP and off-ramp to Key Bridge/Rosslyn
Traffic diverging to ramp
Through-traffic on GWMP
Morning Evening
Peak Hour Peak Hour
(7:00-$:00) (5:00-6:00)
E2
3
D1
Inbound off-ramp to Key Bridge/Rosslyn 3 D4
Traffic on ramp __
Intersection of GWMP off-ramp and North Lynn Street 1
Traffic turning right from ramp to Key Bridge -- D
Traffic from ramp proceeding across Lynn Street --3 E
Inbound off-ramp to Roosevelt Bridge 5
Traffic on ramp F B
Junction of inbound off-ramp to Roosevelt Bridge and 1-66
Traffic merging from ramp E B
Through-traffic on inbound 1-66 D A
Outbound GWMP between Roosevelt and Key bridges
Traffic merging from Roosevelt Bridge ramp B E
Through-traffic on GWMP A D
Intersection of Fort Myer Drive and GWMP on-ramp
All traffic entering intersection A D
Outbound GWMP between Key Bridge and Spout Run
Traffic merging from Key Bridge ramp C F
Traffic diverging to Spout Run Parkway B F
Through-traffic on GWMP B F
1. Due to traffic control measures, this maneuver is unimpeded.
2. Due to traffic control measures, this junction is treated as a two-phase, signalized
intersection.
3. Due to traffic control measures, traffic is not permitted on the ramp.
4. Low level of service is caused by ramp geometrics rather than volume.
5. Traffic on ramp is typically restricted during the morning peak period because of
traffic conditions at the junction with 1-66 and Roosevelt Bridge. By definition, level
of service is F.
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During the evening peak hour, level of service is E or F at the following
locations:
junction of the on-ramp from Roosevelt Bridge and outbound GWMP
outbound GWMP between Key Bridge and Spout Run Parkway,
including the junction of outbound GWMP and the on-ramp from Key
Bridge/Rosslyn
intersection of North Lynn Street and the off-ramp from inbound
GWMP
intersection of Lorcom Lane and Spout Run Parkway
VEHICLE OCCUPANCY
Vehicle occupancy is an indicator of the degree to which commuters, in
particular, either carpool or vanpool to and from work. The more people
who ride in one vehicle, the more efficiently the road system can serve
the commuter demand. Vehicle-occupancy counts of vehicles crossing into
the central business district were conducted in the fall of 1981 and the
spring of 1983, and the data were compared (table 12). In the two-year
period, the number of persons traveling into the Washington, D.C.,
central business district had increased 5 percent; the number of
single-occupant automobiles had increased by 15 percent; carpool
ridership had increased by 6 percent; and vanpool ridership had
increased by 100 percent. Similar counts were made of vehicles crossing
the Capital Beltway (1-495/95) in the fall of 1981 and the spring of 1984.
These data showed that the number of persons crossing the beltway had
increased by 24 percent; carpool ridership had increased slightly; and
vanpool ridership in the morning rush hours had increased by 118
percent.
Ridesharing on GWMP and Spout Run Parkway was lower than the average
for all the roadways studied. In 1981, the average vehicle occupancy
recorded at a counting station on GWMP between Spout Run and Key
Bridge was 1.43 persons per vehicle, compared to an average occupancy
of 1.48 for all the stations in the study. Similar data for Spout Run
Parkway, gathered in 1982, showed roughly the same vehicle-occupancy
rate as for GWMP. In 1983 the average vehicle occupancy recorded at the
GWMP station was 1.26, compared to an average rate of 1.47 for all
stations.
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Table 12: Vehicle occupancy, 1981-1982
Average Vehicle Occupancy
Percent
Single Occupany
1981
1982
1983
1984
1981
1982
1983
1984
Capital Beltway (1-495/95)
cordon line
All stations
6:30 to 9:30 a.m.
1.30a
1.33b
80.1a
80.1b
GWMP
6:30 to 9:30 a.m.
1.35a
1.31b
76.5a
79.3b
GWMP (between beltway
and Dead Run Creek)
6:00 to 9:15 a.m.
1.26c
80.Oc
GWMP (between beltway
and Dead Run Creek)
3:30 to 6:25 p.m.
1.39c
75.8c
Core (central business
district) cordon line
All stations
6:30 to 9:30 a.m.
1.48d
--
1.47e
67.6d
--
70.4e
GWMP
6:30 to 9:30 a.m.
1.43d
--
1.26e
68.64
--
80.9e
GWMP (north of Spout
Run)
f
6:30 to 9:30 a.m.
--
1.43f
73.2
Spout Run
6:30 to 9:30 a.m.
--
1.429
--
69.18
Spout Run
4:00 to 6:30 p.m.
--
1.419
--
69.3g
--
Sources:
a. MWCOG fall 1981 beltway cordon count
b. MWCOG spring 1984 beltway cordon count
c. VDH&T count on September 22, 1982
d. MWCOG spring 1981 core cordon count
e. MWCOG spring 1983 core cordon count
f. MWCOG count on November 11, 1982
g. NPS, DSC, count on November 9, 1982
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Environmental Consequences
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IMPACTS ON PARKWAY VALUES
VISUAL QUALITY
The most significant potential for impacts on scenic quality would occur at
the Spout Run merge (inbound), near Key Bridge, and across from the
Theodore Roosevelt Island parking lot. Sketches have been provided to
show how the construction of retaining walls in alternatives C and D
would considerably alter the character of the parkway. To mitigate the
impact wherever retaining walls were used, their height would be
restricted to between 3 and 4 feet wherever possible, they would be faced
with rock, and appropriate plant materials would be added where space
was available.
Cut and fill would also detract from scenic values by disturbing the
established vegetation. This impact is addressed under "Natural
Resources," below.
During the preliminary design phase, and on a case-by-case basis, each
road section would be evaluated for the applicability and use of cut-and-
fill slopes or retaining walls or a combination of the two. The cross
sections included in this report are intended to generally illustrate the
probable magnitude of the visual change at specific locations along the
parkway.
Alternative A
The visual quality of the parkway would be enhanced by rebuilding the
curbs, putting a rock face on the Key Bridge on-ramp abutment,
developing and implementing a landscape plan, and replacing the existing
guardrails with less obtrusive materials. The use of reflective markings,
guardrails, and signs to improve traffic safety would have a minor
adverse effect on the visual quality of the parkways. Standards for
protecting parkway values would be developed in the future, and all
safety and other improvements would conform with the standards. During
the period when roadwork was in progress, the signs needed to route
traffic would create a short-term adverse effect on scenic quality.
Alternative B
The structural changes included in alternative B would result in a
moderate change in the aesthetic character of the parkway. Overall, 3.74
acres of greenspace--grass, shrubs, and trees--would be replaced with
paved surfaces to extend the acceleration and deceleration lanes for the
ramps and merge areas, add a third lane to outbound GWMP between Key
Bridge and Spout Run, improve the access to the Theodore Roosevelt
Island parking lot, and reconstruct the Key Bridge off-ramp. A more
detailed description of the vegetation loss is included under "Natural
Resources," below.
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Widening portions of GWMP from two to three lanes would create a
significant visual change. There would be a further highly noticeable
change created by the loss of the tree canopy along the new 1,200-foot
Spout Run/GWMP merge area. The construction of a third lane over the
rock escarpment at the Spout Run merge would open up a key view of the
river and the Georgetown waterfront.
The Key bridge off-ramp improvement and the lengthened deceleration
lane at Roosevelt Bridge would have no significant visual impact.
Alternative C
The visual impacts described for alternative B would be more extensive
under this alternative. Overall, 4.19 acres of greenspace would be
replaced with paved surfaces. The third inbound lane originating at
Spout Run would extend all the way to the Key Bridge/Rosslyn Circle
off-ramp, resulting in the loss of an additional 2,400 linear feet of
landscaped area. The new stacking lane for the off-ramp to Roosevelt
Bridge would be constructed on a steep wooded embankment that
currently serves as an important visual buffer between the commercial
highrise buildings of Rosslyn and the parkway corridor and Theodore
Roosevelt Island. The construction of the new ramp would result in the
removal of some 500 linear feet of this woodland barrier. Some
post-construction landscaping would be accomplished, but the wooded
screen serving to buffer the commercial appearance of Rosslyn would be
lost and could not be replaced. This would constitute a severe adverse
effect on the aesthetic qualities of GWMP and Theodore Roosevelt Island.
Alternative D
Alternative D would have the most severe impacts on scenic values. A
total of 4.93 acres would be converted from greenspace to paved surfaces
in the course of adding new third lanes to the entire length of both the
inbound and the outbound roadways and a new fourth lane to outbound
GWMP between Key Bridge and Spout Run. The parkway's visual and
spatial organization would be considerably altered by its conversion to a
six-lane freeway. The ratio of paved surfaces to greenspace would
change considerably with a 33 percent increase in pavement over what
now exists, and many pictorial elements--vegetative screens, frames,
dividers, and borders--would be lost. In addition to the impacts
described for alternatives B and C, the construction of a new off-ramp to
Key Bridge would require the replacement of a steep wooded embankment
with a double wall 30 feet high, destroying a natural landform and
introducing a massive structural element that would be evident to parkway
travelers and pedestrians on Key Bridge. The cumulative effect of all
these actions would be to destroy the relationship between the roadway
and the natural landscape. Thus, the traditional concept of the parkway
being parkland containing a road, and not just a roadway, would be lost.
The former parkway would be reduced to an urban interstate with
landscaping.
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Inbound view Theodore Roosevelt Island and 1-66 bridge.
Parkway values: Treed parkway edges and median are
effective buffers for park users. The thinly wooded sloped
bank to the right barely buffers 1-66 and the commercial
development adjoining in Rosslyn. Parkway right-of-way
opposite Theodore Roosevelt Memorial is very narrow. Any
major new construction will negate park values that are
fragile in this zone. Post construction landscape restoration
measures will offer little to mitigate.
Existing view Theodore Roosevelt Island parking lot to
Rosslyn offscape. Parkway value: Thin vegetative cover as
shown across from the Theodore Roosevelt Island parking
area that provides a screen for the massive scale of the
Rosslyn commercial area and adjacent 1-66 right-of-way. Also
important in retaining parkway character in this narrow
roadway segment and for enhancing scenic views from
Theodore Roosevelt Island and pedestrian bridge.
Parkway's on ramp from the Theodore Roosevelt Bridge will
result in the loss of approximately 1,000 feet of grass area.
An additional 1,000 feet of grass median will also be lost as a
result of the construction of new acceleration and
deceleration lanes in and out of the Theodore Roosevelt
Memorial parking area.
Some foreground green space along outbound parkway
would be lost due to lengthened acceleration lane coming off
of Theodore Roosevelt Bridge as well as improved
acceleration and deceleration lanes in and out of parking
area.
Same construction features as alternative B, with the
difference as follows: the inbound off ramp (stacking lane)
to 1-66 would severely impact the thinly wooded steep bank.
The wooded screen would be removed, the slope regraded to
accommodate the off ramp and two retaining walls would be
required to stabilize the sloping ground. The parkway would
lose an important buffer now shielding the Theodore
Roosevelt Memorial Island complex. Though mitigation
through some replanting is possible, the parkway's right-of-
way is too crimped to allow replacement through use of
mature trees.
Through this segment of alternative C. parkway character is
transformed into an urban expressway. The fragile vegetation
that separates 1-66 and Rosslyn can no longer be retained to
accommodate lane widening and the 1-66 off ramp (stacking
lane) with attendent retaining walls. The outbound parkway
impacts in this view would be the same as alternative B.
In alternative D, the lengthening of the 1-66 off ramp would
require a 500-foot retaining wall along the inbound roadway
to be placed into the slope to create the extra lane. In this
stretch, the parkway would total three lanes inbound and
three lanes outbound, plus the added acceleration and
deceleration lanes into the Theodore Roosevelt Memorial
Island parking lot. Much of the vegetated median would also
be lost.
Inbound, the existing Rosslyn vegetative screen will be lost
due to retaining walls and removal of mature trees and other
vegetation that will be required to add a third lane into the
Theodore Roosevelt Bridge on-ramp. Outbound, the existing
vegetated median will also need to be removed. Here, another
retaining wall will be required so as to minimize the area used
on the foreground side of the parkway. This is done so as to
not further narrow the Theodore Roosevelt Island parking
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Key Bridge (inbound). Parkway value: At Key Bridge, a focal
parkway feature, the park assumes two distinct experiential
units. Northward, the more rural parkway traverses
suburban/rural countryside; the palisades, and the Potomac
Valley. Offscapes of the natural landscape feature
Georgetown and National Capital monuments. Southward,
the parkway bisects a convuluted network of highways, and
widens out as it transects denser land use, National Airport,
and numerous bridges into the District of Columbia. Major
elements at Key Bridge that distinguish parkway character
are balance between structural and landscape elements, the
wide median and grade differential between lanes, the
sweeping curve, and generous greensward of grass and mass
plantings. Despite past construction, the parkway retains
these distinguishing characteristics parkways are noted for.
Changes to parkway will result in alternatives B and C by
widening of the inbound lane to add a deceleration ramp for
the Key Bridge off ramp. Some loss of median is required to
maintain two lane flow of inbound traffic. However, parkway
character remains largely intact in this parkway segment
under both alternatives.
SAME AS ALTERNATIVE B
Alternative D requires extensive alteration to historic
parkway scale; from parkway to an urban expressway, with
landscaping - six lanes overall flow inbound and outbound.
A seventh lane at Key Bridge facilitates off parkway traffic to
Key Bridge. Parkway is taking on an interstate appearance
that completely departs from historical distinguishing
character. In this parkway segment, the existing vegetated
median would be lost and paved surfaces would dominate the
view of the parkway user.
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ALTERNATIVE C
VIEW OF STACKING LANE OFF INBOUND PARKWAY
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ALTERNATIVES C AND D
VIEW OF INBOUND PARKWAY ACROSS FROM
THEODORE ROOSEVELT ISLAND PARKING AREA
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ALTERNATIVE D
OUTBOUND PARKWAY BELOW KEY BRIDGE
ALTERNATIVES B AND C
OUTBOUND PARKWAY BELOW KEY BRIDGE
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ALTERNATIVE D
NEW OFF RAMP TO ROSSLYN CIRCLE FROM
INBOUND PARKWAY WITH R.O.W. PURCHASE
ALTERNATIVE D
NEW OFF RAMP TO ROSSLYN CIRCLE
FROM INBOUND PARKWAY WITHOUT R.O.W.
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ALTERNATIVES C AND D
OUTBOUND PARKWAY IMMEDIATELY
PRIOR TO SPOUT RUN EXIT
ALTERNATIVE B
OUTBOUND PARKWAY IMMEDIATELY
PRIOR TO SPOUT RUN EXIT
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ALTERNATIVE B
INBOUND PARKWAY AT SPOUT RUN MERGE
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ALTERNATIVES C AND D
INBOUND PARKWAY AT SPOUT RUN MERGE
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ADDITIONAL INBOUND LANE EXITING AT THEODORE ROOSEVELT
BRIDGE (ALTERNATIVE D)
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VIEW OF INBOUND PARKWAY JUST PAST SPOUT RUN MERGE
(ALTERNATIVES B, C, D)
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NEW INBOUND EXIT RAMP TO ROSSLYN ADJACENT TO GEORGE
WASHINGTON MEMORIAL PARKWAY ON-RAMP FROM KEY BRIDGE
(ALTERNATIVE D)
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LANE TO RIVER SIDE OUTBOUND GEORCf
MEMORIAL PARKWAY APPROACH 1NG
ATIVE B)
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 Approved For Release 2010/05/17: CIA-RDP89-00244R001002410011-7
VIEW OUTBOUND UNDER KEY BRIDGE. ONE LANE INBOUND
WIDENING AT KEY BRIDGE EXIT TO ROSSLYN AT FAR LEFT.
(ALTERNATIVES B, C)
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NATURAL RESOURCES
Alternative A
Resurfacing of the roadway and construction of safety improvements would
have little or no effect on soils, vegetation, or water conditions. The
projected increases in traffic would increase the amount of petroleum
based contaminants that would wash from the roadway surface into
wetlands and the Potomac River. Sand and salts used to reduce snowy
or icy roadway conditions would also continue to wash into wetlands and
the river.
An increase in traffic volumes would have no direct effect on vegetation.
The effect on wildlife would be minimal; some increase in road kills of
gray squirrels and other small animals would be expected.
Segments of GWMP and the entrances and parking area for Theodore
Roosevelt Island are in the 100-year floodplain of the Potomac River, and
approximately 3,100 feet of the inbound lanes and 2,200 feet of the
outbound lanes of Spout Run Parkway are in the 100-year floodplain of
Spout Run. The improvements in the roadway surfaces would have no
impacts on floodplains since no roadway geometrics would be changed.
Alternative B
The expansion of the roadway to improve traffic flow and safety would
affect 322,000 square feet (7.41 acres) of soil and vegetation, of which
less than half (3.66 acres) would be restored to some degree with trees,
shrubs, and ground cover. Drainage patterns would be altered, and the
increase in an impervious pavement cover would prevent precipitation from
soaking into the ground. There would be a proportionate increase in the
amount of runoff, which would create erosion problems along drainages
and increase the amount of sediment washed into the Potomac River.
Erosion and sedimentation would be greatest during construction periods
and decrease as vegetation became reestablished on exposed slopes. The
projected increases in traffic would increase the petroleum-based
contaminants washing into wetlands and the Potomac River. Expansion of
the roadway surface would require increased amounts of sand and salts to
reduce snowy or icy conditions, and these additional contaminants would
also wash into wetlands and the river.
The primary impacts on vegetation would be the permanent removal of
3.74 acres of grass and woodland vegetation and the disturbance of an
additional 3.66 acres. Some of this acreage was previously disturbed and
landscaped during the original construction of the parkway. Of the
acreag6 affected by the current action, 3.66 acres would be relandscaped
and planted to grass and native shrubs and trees. An additional 13,600
square feet (0.31 acre) of existing pavement would be removed and
planted to grass or native shrubs and trees.
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The numbers of trees that would be removed by specific actions are
shown in table 13. The numbers were obtained by actual counts. The
road cuts, paved areas, and other features of each alternative were
staked on site so that accurate counts and measurements could be taken.
A complete assessment of impacts on trees, including a breakdown of tree
types, is available at the parkway headquarters at Turkey Run, Virginia.
The numbers of trees listed in table 13 represent worst-case analyses of
the maximum cuts and fills required to accommodate roadway changes. If
retaining walls were more extensively used to decrease cut-and-fill slopes,
fewer trees would be affected. However, fill slopes would offer the
advantage of allowing for revegetation. During the preliminary design
phase, the most appropriate combination of required cut-and-fill slopes
and retaining walls would be identified, and impacts would be minimized
wherever possible.
The vegetation disturbance caused by construction would interfere with
the natural vegetative succession. The forest in this segment of the
parkway is currently in transition. The present dominant tree types,
including tulip poplar and black locust, are giving way to the more
desirable climax vegetation types, represented by the oak, maple, and
beech saplings that are now appearing along the forest floor. Any
disturbance of these communities would eliminate between 30 and 40 years
of natural succession. This impact would be mitigated by using
second-succession-phase plant materials and trees in sufficient quantities
to properly recover the slopes. Larger trees that were balled in burlap
would be used wherever feasible to shorten the time it would take for
recovery of mature conditions. Wherever cut slopes were too steep to use
larger stock, bare root plantings, or whips, would be used and the
recovery time would be longer.
The removal of woodland vegetation would reduce some habitat available to
woodland wildlife species. The parkway and adjoining areas of Arlington
have limited woodlands, and there would be no place for these animals to
relocate. Road kills could increase as a result of greater traffic volumes.
The cumulative effect of reduced habitat and increased road kills would
reduce the populations of small animals in this section of the parkway.
Approximately 400 feet of the inbound lanes and 1,400 feet of the
outbound lanes of GWMP and the entrance and parking area for Theodore
Roosevelt Island are in the 100-year floodplain of the Potomac River. The
extension of the acceleration lane for outbound traffic from Roosevelt
Bridge, the modification of the access and parking area for Theodore
Roosevelt Island, and the realignment of the inbound and outbound lanes
would occur in the 100-year floodplain. Some increases in grade would be
made for these roadway changes. The addition of a third outbound lane
between Key Bridge and Spout Run (1,450 feet) would require the
construction of retaining walls in the 100-year floodplain. This
development would alter the configuration of the floodplain, obstruct the
floodway, and displace some floodwaters to other areas of the Potomac
River floodplain. The selection of alternative B would require preparation
of a statement of finding to document the rationale for the determination
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Table 13: Summary of Tree Removals
Alternative B
No.
Total Diameter (inches)
Inbound: Spout Run merge to
Key Bridge, right side
417
4,556.0
Inbound: Key Bridge to Roosevelt
Bridge, right side
225
1,431.0
Outbound: Theodore Roosevelt Island
north area to Spout Run exit
78
1,167.0
Total
720
7,154.0
Alternative C
Inbound: Spout Run merge to
Key Bridge, left side
116
1,368.0
Inbound: Spout Run merge to
Key Bridge, right side
194
2,013.0
Inbound: Key Bridge to Roosevelt
Bridge, right side
77
1,008.0
Outbound: Theodore Roosevelt Island
north area to Spout Run exit
109
1,842.5
Total
496
6,231.5
Alernative D
Inbound: Spout Run merge to
Key Bridge, left side
116
1,368.0
Inbound: Spout Run merge to
Key Bridge, right side
194
2,013.0
Inbound: Ramp to Rosslyn Circle
along Marriot tract
239
2,558.5
Inbound: Key Bridge to Roosevelt
Bridge, right side
221
2,605.0
Outbound: Theodore Roosevelt Island
north area to Spout Run exit
270
4,185.0
1,040
12,729.5
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that there is no practicable alternative to expanding the roadway in the
floodplain. During any flooding conditions on the parkway, the U.S.
Park Police would reroute traffic as necessary. No critical actions would
occur in the 500-year floodplain. The construction of a third outbound
lane along the piedmont rock cliff would force the development of the
Potomac River Trail onto the river edge, which would have an indirect
effect on wetlands of the river.
Alternative C
The addition of inbound and outbound lanes to improve traffic flow and
safety would affect 411,000 square feet (9.44 acres) of soil and
vegetation, of which more than half (5.25 acres) would be restored to
some degree with trees, shrubs, and ground cover. Drainage patterns
would be altered, and the increase in an impervious pavement cover would
prevent precipitation from soaking into the ground. There would be a
proportionate increase in the amount of runoff, which would create
erosion problems along drainages and increase the amount of sediment
washed into the Potomac River. Erosion and sedimentation would be
greatest during construction periods and decrease as vegetation became
reestablished on exposed slopes. The projected increases in traffic would
increase the petroleum-based contaminants washing into wetlands and the
Potomac River. Expansion of the roadway surface would require
increased amounts of sand and salts to reduce snowy or icy conditions,
and these additional contaminants would also wash into wetlands and the
river.
The primary impacts on vegetation in this section of the parkway would
be the permanent removal of 4.19 acres of grass and woodland vegetation
and the disturbance of an additional 5.25 acres. Some of this acreage
was previously disturbed and landscaped. Of the acreage affected by the
current action, 5.25 acres would be relandscaped and planted to grass
and native shrubs and trees. An additional 20,800 square feet (0.48
acre) of existing pavement would be removed and planted to grass or
native shrubs and trees. The numbers of trees that would be removed
are shown in table 13. As described for alternative B, the impacts on
vegetation would include a 30- to 40-year setback in natural succession on
disturbed sites that would be revegetated.
The removal of woodland vegetation would reduce some habitat available to
woodland wildlife species. The parkway and adjoining areas of Arlington
have limited woodlands, and there would be no place for these animals to
relocate. Road kills could increase as a result of greater traffic volumes.
The cumulative effect of reduced habitat and increased road kills would
reduce the animal populations in this section of the parkway.
Approximately 400 feet of the inbound lanes and 1,400 feet of the
outbound lanes of GWMP and the entrance and parking area for Theodore
Roosevelt Island are in the 100-year floodplain of the Potomac River. The
extension of the acceleration lane for outbound traffic from Roosevelt
Bridge, the modification of the access and parking area for Theodore
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Roosevelt Island, and the realignment of the inbound and outbound lanes
would occur in the 100-year floodplain. Some increases in grade would be
made for these roadway changes. The addition of third and fourth
outbound lanes between Key Bridge and Spout Run (1,450 feet) would
require the construction of retaining walls in the 100-year floodplain.
This development would alter the configuration of the floodplain, obstruct
the floodway, and displace floodwaters to other areas of the Potomac
River floodplain. The selection of alternative C would require preparation
of a statement of finding to document the rationale for the determination
that there is no practicable alternative to expanding the roadway in the
floodplain. During any flooding conditions on the parkway, the U.S.
Park Police would reroute traffic as necessary. No critical actions would
occur in the 500-year floodplain. The construction of two additional lanes
for outbound traffic along the piedmont rock cliff would force the
development of the Potomac River Trail farther onto the river edge, which
would have an indirect effect on wetlands of the river.
Alternative D
The addition of inbound and outbound traffic lanes and ramp changes to
improve traffic flow and safety would affect 624,000 square feet (14.33
acres) of soil and vegetation, of which approximately two thirds (9.40
acres) would be restored to some degree with trees, shrubs, and ground
cover. Drainage patterns would be altered, and the increase in an
impervious pavement cover would prevent precipitation from soaking into
the ground. There would be a proportionate increase in the amount of
runoff, which would create erosion problems along drainages and increase
the amount of sediment washed into the Potomac River. Erosion and
sedimentation would be greatest during construction periods and decrease
as vegetation became reestablished on exposed slopes. The projected
increases in traffic would increase the petroleum-based contaminants
washing into wetlands and the Potomac River. Expansion of the roadway
surface would require increased amounts of sand and salts to reduce
snowy or icy road conditions, and these additional contaminants would
also wash into wetlands and the river.
The primary impacts on vegetation would be the permanent removal of
4.93 acres of grass and woodland vegetation and the disturbance of an
additional 9.40 acres. Some of this acreage was previously disturbed and
landscaped. Of the acreage disturbed by the current action, 9.40 acres
would be relandscaped and planted to grass and native shrubs and trees.
An additional 13,600 square feet (0.31 acre) of existing pavement would
be removed and planted to grass or native shrubs and trees. The
numbers of trees that would be removed are shown in table 13. As
described for alternative B, impacts on vegetation would include a 30- to
40-year setback in natural succession for disturbed sites that would be
revegetated.
The removal of woodland vegetation would reduce some habitat available to
woodland wildlife species. The parkway and adjoining areas of Arlington
have limited woodlands, and there would be no place for these animals to
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relocate. Road kills could increase as a result of greater traffic volumes.
The cumulative effect of reduced habitat and increased road kills would
reduce the animal populations in this section of the parkway.
Approximately 400 feet of the inbound lanes and 1,400 feet of the
outbound lanes of GWMP and the entrance and parking area for Theodore
Roosevelt Island are in the 100-year floodplain of the Potomac River. The
extension of the acceleration lane for outbound traffic from Roosevelt
Bridge, the modification of the access and parking area for Theodore
Roosevelt Island, and the realignment of the inbound and outbound lanes
would occur in the 100-year floodplain. Some increases in grade would be
made for these roadway changes. The addition of third and fourth
outbound lanes between Roosevelt Bridge and Spout Run would require
construction of retaining walls in the 100-year floodplain. This
development would alter the configuration of the floodplain, obstruct the
floodway, and displace floodwaters to other areas of the Potomac River
floodplain. The selection of alternative D would require preparation of a
statement of finding to document the rationale for the determination that
there is no practicable alternative to expanding the roadway in the
floodplain. During any flooding conditions on the parkway, the U.S.
Park Police would reroute traffic as necessary. No critical actions would
occur in the 500-year floodplain. The construction of two additional lanes
for outbound traffic along the piedmont rock cliff would force the
development of the Potomac River Trail onto the river edge, which would
have an indirect effect on wetlands of the river.
The expansion of the roadway to four lanes between Key Bridge and the
Spout Run exit could require a permit from the U.S. Army Corps of
Engineers for development of a retaining wall and fill along the Potomac
River.
AIR QUALITY
The CALINE 3 model was used to predict carbon monoxide levels for four
sites where people might be present for long periods. The predicted
one-hour (morning and evening peak hour) concentrations of carbon
monoxide are listed in table 14, and the predicted eight-hour
concentrations are listed in table 15. No instances of violations of the
national ambient air quality standards for carbon monoxide would be
expected. Alternative A would result in the most adverse impact because
of the more congested road conditions and slower speeds. Impacts would
be greatest during the evening peak period at all four receptor sites.
The Theodore Roosevelt Island parking lot would receive the highest
carbon monoxide concentrations in both 1990 and 2000. Alternatives B,
C, and D would not vary greatly in the general levels of concentration;
however, some localized differences would occur. For example, elevated
concentrations in the vicnity of the Marriott Hotel would occur under
alternative D as a result of the additional off-ramp leading from inbound
GWMP to Rosslyn Circle.
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Table 14: Predicted Carbon Monoxide One-Hour Concentrations,
1990 and 2000
Alternative Alternative
A B C D A B C D
1990 Morning 1990 Evening
Receptor Site Peak Hour (ppm) Peak Hour (ppm)
Lorcom Lane and 3.0 2.9 2.8 2.7 5.9 2.9 3.0 3.0
Spout Run
Lee Highway and 3.3 3.1 2.8 2.8 4.9 3.1 3.0 3.0
Adams Street
Marriott Hotel 3.3 3.2 3.1 3.5 5.7 3.3 3.4 3.5
Theodore Roosevelt 3.8 3.6 3.7 3.8 10.3 4.3 4.2 4.0
Island parking lot
2000 Morning 2000 Evening
Peak Hour (ppm) Peak Hour (ppm)
Lorcom Lane and 2.5 2.4 2.5 2.3 4.6 2.7 2.7 2.7
Spout Run
Lee Highway and 2.6 2.6 2.4 2.4 3.8 2.7 2.7 2.8
Adams Street
Marriott Hotel 2.8 2.7 2.8 3.0 4.3 2.8 2.8 3.0
Theodore Roosevelt 3.1 3.1 3.4 3.4 7.6 3.5 3.5 3.4
Island parking lot
Source: Belomo-McGee 1984.
Note: The carbon monoxide standard for one hour is 35.0 ppm.
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Table 15: Predicted Carbon Monoxide Eight-Hour Concentrations,
1990 and 2000
Alternative
Receptor Site
A
B C
D
1990 (ppm)
Lorcom Lane and Spout Run
4.1
2.0 2.1
2.1
Lee Highway and Adams Street
3.7
2.4 2.2
2.2
Marriott Hotel
4.0
2.3 2.4
2.4
Theodore Roosevelt Island parking
lot
7.2
3.0 2.9
2.8
2000 (ppm)
Lorcom Lane and Spout Run
3.2
1.7 1.9
1.9
Lee Highway and Adams Street
2.9
2.1 2.1
2.2
Marriott Hotel
3.0
1.9 1.9
2.1
Theodore Roosevelt Island parking
lot
5.3
2.4 2.4
2.4
Source: Bellomo-McGee 1984.
Note: The carbon monoxide eight-hour standard is 9.0 ppm.
The predicted hydrocarbon emission burdens that would occur under the
various alternatives are compared in table 16. There would be little
difference among the alternatives with regard to the hydrocarbon regional
burden.
Some short-term adverse air quality effects would result from construction
activities. The alternatives calling for major new construction or
reconstruction--alternatives C and D--would potentially have the most
detrimental impacts. Adverse effects on air quality would result from
delays on the road system; from fugitive dust caused by grading, earth
moving, and demolition activities; and from additional trips generated by
construction vehicles. None of these sources would have long-term or
irreversible effects on air quality, and the impacts could be mitigated
using effective work zone traffic control measures and standard
procedures for watering and other methods of dust control.
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Table 16: Hydrocarbon Burden Analysis, 1990 and 2000
Regional Peak Hour Hydrocarbon Emissions
(100 lb/hour)
Alternative
Morning
Evening
Morning
Evening
A
17.6
15.7
10.4
9.3
B
17.6
15.7
10.4
9.3
C
17.6
15.7
10.4
9.3
D
17.6
15.7
10.4
9.3
Note: Predictions of peak-hour emissions are based on morning
and evening peak-hour vehicle miles of travel and average speed.
In summary, none of the alternatives would adversely affect air quality in
the metropolitan Washington area, with the possible exception of some
short-term carbon monoxide effects during construction. The national
ambient air quality standards for carbon monoxide are not currently being
violated in the northern Virginia portion of the region, and none of the
GWMP alternatives would result in violations of the standards in the
future. The regional ozone standard is expected to be attained by 1987
with the implementation of federal controls on motor vehicles and the
inspection and maintenance programs being implemented in Virginia, the
District of Columbia, and Maryland, together with the program for
stationary source controls in these areas.
Regional proposals for attaining conformance with the national ambient air
quality standards are outlined in a "Final Washington Metropolitan Air
Quality Plan for Control of Ozone and Carbon Monoxide" (MWCOG 1982).
This is a required state implementation plan and it has been approved by
the Environmental Protection Agency. The FHWA has determined that
both the transportation plan and the transportation improvement plan
conform with the state implementation plan. FHWA has also determined
that this project is included in the transportation improvement program
for the metropolitan Washington region. Therefore, pursuant to 23 CFR
770, this project conforms to the state implementation plan.
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NOISE
The FHWA traffic noise prediction model was used to predict the
traffic-generated noise levels for four sites where people might be present
for long periods. The results of this analysis, shown in table 17,
indicate that future noise levels would be slightly higher than existing
levels as a direct result of increased traffic volumes and speeds. The
predicted traffic-generated noise levels do not include ambient sound
generated from other sources, most prominently the jet aircraft using
National Airport, which would undoubtedly continue to dominate noise
levels in the GWMP study area.
Traffic-generated noise would differ slightly among the alternatives. The
predicted noise levels would be within the FHWA design noise level with
the exception of one reading for the Theodore Roosevelt island parking
lot. This site would receive the highest noise impacts under all of the
alternatives because of its proximity to the roadway and the unbuffered
conditions. The FHWA design level for this land use (67 L ) would be
slightly exceeded at this site in the evening peak hour by fhe year 2000
as a result of additional traffic on the added outbound lane proposed in
alternative D. It might be desirable to construct a landscape berm as a
sound attenuation barrier in the Theodore Roosevelt Island parking lot.
This could enhance the park experience for visitors and the visual
experience for parkway users.
The residential area on Lee Highway at Adams Street would receive
greater impacts than the Lorcom Lane residential area because it is closer
to the roadway. The Marriott Hotel receptor site would generally receive
the least impact because of its distance from the roadway.
CULTURAL RESOURCES
The historic character of the parkway would be affected by changes in
the roadway alignment. The impact is addressed under "Visual Quality."
No other historic resources would be adversely affected under any of the
alternatives. Construction activities under alternatives B, C, and D
would require archeological surveying and testing. The potential for
disturbance of archeological resources would be minimal in alternative B,
moderate in alternative C, and high in alternative D.
If any unanticipated archeological remains were discovered during the
construction phases of this project, construction would halt and the
regional archeologist of the National Capital Region would be notified
immediately in order to make an on-site determination of the nature and
significance of the archeological remains.
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Table 17:
Predicted Traffic Noise impacts, 1990 and 2000
Alternative
Alternative
A B C D
A B C D
1990 Morning Peak-Hour (Leq(h))
1990 Evening Peak-Hour (Leq ))
Lorcom Lane and Spout
Run
53.0
53.4
56.4
55.5
58.2
58.1
58.3
58.1
Lee Highway and Adams
Street
65.3
65.2
64.8
64.8
66.2
66.2
66.3
66.2
Theodore Roosevelt
Island parking lot
63.3
64.3
64.5
65.0
62.4
64.7
64.9
67.0
2000 Morning Peak-Hour (Leq(h))
2000 Evening Peak-Hour (Leq(h))
Lorcom Lane and Spout
Run
56.6
56.9
58.9
58.2
59.3
59.3
60.5
60.8
Lee Highway and Adams
Street
65.9
65.8
64.8
64.8
66.9
66.9
66.9
66.9
Theodore Roosevelt
Island parking lot
63.8
64.8
65.0
65.2
63.0
65.6
65.9
67.9
Note: The FHWA design noise level for the affected land uses is 67.0 Leq.
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RECREATION
Alternative A
An improved road surface would add to the pleasure of driving the
parkway and, in that respect, increase its recreational value. Otherwise,
this alternative would have no significant effect on recreation within the
study area.
Alternative B
The reconstruction of Rosslyn Circle and the GWMP off-ramp to the circle
and Key Bridge would improve traffic flow and create safer and less
confusing crossings for pedestrians and bicyclists. The installation of a
traffic signal at the intersection of the GWMP off-ramp and Lee Highway
would regulate bicycle traffic on the bicycle path and would ensure safe
crossings for motorists and bicyclists.
Improvements to the Theodore Roosevelt Island parking area, such as
acceleration/deceleration lanes, new entrance, redesigned lot, and
landscaping, would make that site a more attractive and safer area for
visitors, and it might increase the recreational use of the site by 10
percent or more. Further increases in recreational use would be expected
to accompany additional planned improvements, such as extending the
Mount Vernon Trail, building a bicycle/pedestrian bridge to Rosslyn, and
providing restrooms, trash cans, and picnic tables. When all of this
other development is completed, recreational use is expected to increase
by 100 to 200 percent.
Adding a continuous lane on outbound GWMP between the on-ramp from
Key Bridge/Rosslyn and the Spout Run exit would require paving part of
the narrow strip of land between the roadway and the river. This would
encroach on the Potomac River Trail and bring traffic closer to hikers.
Because of the narrowness of this section, the natural character of the
trail is already compromised, and this action would only add further to
the intrusive visibility, noise, and hazard of traffic.
Alternative C
A fourth outbound lane between the Key Bridge on-ramp and the Spout
Run exit would encroach even closer than alternative C on the existing
hiking trail. To accomplish the road widening in the narrowest sections,
retaining walls and landfill would be required, and the hiking trail would
be routed onto boardwalks at the base of the wall. Other impacts of this
alternative would be the same as described for alternative B.
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Alternative D
The addition of a third continuous lane between Roosevelt and Key
Bridges would confine the Little River shoreline recreational activity to a
narrower area. Other impacts of this alternative would be the same as
those described for alternatives B and C.
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TRAFFIC IMPACTS
INTRODUCTION
The impact analysis involved the use of Metropolitan Washington Council
of Governments travel data, socioeconomic data, and computer coded
networks to measure the effects of each of the alternatives on the entire
metropolitan highway and transit network. The methodology used for this
analysis is described in appendix B. The analysis looked at both the
short-term (1990) and the long-term (2000) impacts of the alternatives
under study.
Because the analysis dealt with conditions in future years, it was
necessary to make some assumptions about those conditions in terms both
of physical growth and development and of policy changes. The following
assumptions, defined by the Metropolitan Washington Council of
Governments, were used in forecasting traffic volumes for GWMP and
Spout Run Parkway for the years 1990 and 2000:
Highways
The Springfield Bypass would be constructed from state route VA 7
to US 1.
The intercounty connector would be constructed from the
Baltimore-Washington Parkway to MD 28 (Darnestown Road).
1-370 would be constructed from Great Seneca Highway to the Shady
Grove Metro station.
The Dulles Toll Road (parallel to the Dulles access road) would be
constructed from VA 28 to the Capital Beltway (I-495).*
Great Seneca Highway would be constructed from Middlebrook Road
to MD 28 (Darnestown Road) in Montgomery County.
MD 228 would be constructed from Indian Head Highway (MD 210) to
the Charles County line in Prince Georges County.
1-495 (Capital Beltway) would be widened to eight lanes from GWMP
to the Cabin John Bridge in Virginia.
High-occupancy-vehicle restrictions would be enforced on 1-66 and
1-395 (Shirley Highway) for reserved lanes during rush hours.
Transit
The 101-mile regional Metrorail system would be complete.
*This road was opened in January 1985.
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OVERVIEW
Most locations within the study area are capacity deficient now, and there
would be little change in this situation as a result of implementing any of
the alternatives (table 18). (A location would be considered capacity
deficient if the level of service was E or F; locations providing levels of
service A through D would not be considered capacity deficient.) Most
locations would remain capacity deficient when roadway improvements were
made because additional traffic would be attracted to the improved
roadway until the greater capacity was reached and congestion again
resulted in a low level of service.
Table 18: Summary of Capacity-Deficient Locations, 2000
Existing
Alternatives
Route Segment
Conditions
A
B
C
D
Inbound/Morning Peak Hour
Junction of Spout Run Parkway and
X
X
X
X
GWMP
GWMP off-ramp to Key Bridge/Rosslyn
--*
--*
--*
X
X
Junction of GWMP off-ramp to Key
--*
--*
--*
X
X
Bridge/Rosslyn and Lynn Street
Junction of GWMP off-ramp to Roosevelt
X
X
X
X
X
Bridge and inbound 1-66
Outbound/Evening Peak Hour
GWMP on-ramp from Roosevelt Bridge
X
X
X
X
X
Junction of on-ramp from Roosevelt
X
X
X
X
X
Bridge and GWMP
GWMP between Key Bridge and
Spout Run
GWMP on-ramp from Key Bridge/Rosslyn
X
X
X
X
Note: X = location where the level of service would be E or F or where the
assignment would exceed the theoretical capacity.
*Ramp closed to traffic from 7:00 to 9:00 a.m.
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While future changes in accident frequency or severity could not be
specifically quantified, it was assumed that improvements in level of
service would reduce stop-and-go traffic conditions and decrease the
number of rear-end collisions.
The remainder of this section surveys how traffic flow, travel
characteristics, and safety conditions would change at various locations as
a result of the actions under consideration. This overview is based on
more detailed analyses of traffic flow, travel characteristics, level of
service, and accidents, which are presented in subsequent sections of
this report.
Reconstruction and signalization of the Lorcom Lane/Spout Run
intersection (proposed as part of alternatives C and D) would eliminate
the need to close outbound Spout Run beyond Lorcom Lane during the
morning peak period and would create safer conditions for vehicles
turning left from Lorcom Lane onto Spout Run Parkway and for vehicles
turning from the inbound to the outbound roadway at the Spout Run
turnaround.
The reconstruction of the Spout Run/GWMP merge area to provide two
lanes for inbound GWMP traffic and a long acceleration lane for traffic
merging onto GWMP from Spout Run (alternative B) would improve traffic
flow on inbound GWMP during the morning peak period. Traffic queues
would not occur during normal operating conditions on GWMP north of the
Spout Run Parkway. Eliminating stop-and-go traffic on this roadway
section should reduce the number of rear-end accidents. However, this
configuration still would not be able to process the projected traffic at an
acceptable level of service (D) by the year 2000. Traffic on Spout Run
Parkway would still have to merge onto GWMP. Traffic queues on Spout
Run would increase from 0.5 mile at present to 1.1 miles under alternative
B, and there would be additional stop-and-go traffic on that parkway.
(Queue length in this discussion is based on a vehicle density of 100
vehicles per mile per lane. The queues described would be those
expected under normal operating conditions; abnormal conditions caused
by accidents, construction work, or any other event that disrupts traffic
flow would result in different queue configurations.)
The construction of an additional third lane on GWMP to serve merging
traffic from inbound Spout Run Parkway (alternatives C and D) would
likely result in a significant increase in inbound traffic during the
morning peak period on Spout Run Parkway. Level of service D would be
obtained only in alternative C. Traffic queues would not be expected to
occur in alternatives C or D.
Construction of a new off-ramp to Fort Myer Drive (alternative D) would
improve access from GWMP to Rosslyn, especially during the morning peak
period. Drivers on GWMP would no longer have to cross North Lynn
Street, at what is now a frequent accident intersection, to go to Rosslyn.
If implemented with the construction of a new third inbound lane and if
opened during the morning peak period, this new off-ramp would result
in significant increases in traffic volumes on GWMP and would allow a
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significant amount of additional traffic to enter the Rosslyn Circle area.
The level of service would not be improved over existing conditions
between Spout Run and the off-ramp to Key Bridge. In alternatives B
and D the level of service would be expected to be D. There could be
some reduction in the number of rear-end accidents in alternatives B, C,
and D.
Opening the off-ramp to Key Bridge during the morning peak period
(alternatives C and D) would generate additional traffic demand to use
Key Bridge. Additional traffic would result in additional congestion and
accidents at the divergence area on inbound GWMP. Queues of 2.75 miles
would be expected under alternative C, and queues of 2.0 miles under
alternative D, at the Key Bridge off-ramp. Travel times would be
shorter with alternative D than with C for traffic approaching the Key
Bridge off-ramp from GWMP. (Travel time in this discussion includes
both running and delay time.)
Reconstruction of the off-ramp to Key Bridge/Rosslyn (alternatives B, C,
and D) would result in higher levels of service except during the morning
peak hours. During the morning peak hours, the projected level of
service would be F for alternatives C and D.
The poor level of service at the intersection of North Lynn Street and the
off-ramp from GWMP would be improved by any action that would
effectively prohibit vehicles on the ramp from crossing the intersection
without a traffic signal. This could be accomplished by reconstructing
the GWMP off-ramp to provide access only to inbound Key Bridge, while
providing access to Rosslyn some other way (alternatives C and D).
Alternatively, it could be accomplished by reconstructing the off-ramp so
it merges with the 1-66 off-ramp, thus providing access to Rosslyn
through the existing signalized intersection at North Lynn Street
(alternative B). Reconstruction of the roadway providing access from
North Lynn Street to the GWMP on-ramp (alternatives B, C, and D)
would provide more storage space for vehicles desiring to enter GWMP
from Rosslyn. Key Bridge would be expected to have a morning
peak-hour capacity deficiency in all of the alternatives.
Construction of a new third inbound lane between Key and Roosevelt
bridges (alternatives C and D) would provide additional capacity.
However, this capacity would be underutilized if the ramp to Key Bridge
was opened during the morning peak period, because congestion near the
Key Bridge exit would impede through-traffic.
Construction of a longer deceleration lane for the off-ramp to Roosevelt
Bridge (alternative B) might improve traffic flow on GWMP. However, the
traffic projections indicate that traffic would still queue on the off-ramp
to the bridge. If the ramp to Key Bridge remained closed during the
morning peak period, the traffic congestion in this area might still back
up onto GWMP, even with the longer deceleration lane.
Construction of a new off-ramp to Roosevelt Bridge with a connector to
outbound US 50 (alternative C) would further compound problems at the
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off-ramp because an additional 500 vehicles per hour would be added
during the morning peak period. Development of the US 50 connector
would also require cooperation with the Virginia Department of Highways
and Transportation because most of the land area is under the jurisdiction
of the commonwealth of Virginia.
Congestion would continue under all alternatives at the major ramp
junctions (where the ramps from GWMP and US 50 intersect 1-66). The
traffic flowing onto Roosevelt Bridge would exceed the capacity of the
bridge. Consequently, the third lane improvements providing additional
roadway capacity in alternatives C and D would not raise the level of
service. However, the improvements in alternatives C and D would
eliminate the queues for traffic approaching the off-ramp to Roosevelt
Bridge. (These queues would be 2.3 miles under alternatives A and B.)
Travel times on GWMP from a point north of Spout Run to Roosevelt
Bridge would be progressively shorter for alternatives A through D.
Traffic flow during the evening peak hour would continue to be at or
near the capacity of Roosevelt Bridge. Construction of a longer
acceleration lane for the GWMP on-ramp from Roosevelt Bridge and
relocation of the access to the parking area for Theodore Roosevelt Island
(alternatives B and C) would facilitate merging and provide drivers with
a safer area to merge. The addition of a third continuous lane would
reduce congestion at the merge area. This should reduce rear-end
collisions. However, during the evening peak hour, the merge would be
made at a low level of service (E) under all of the alternatives.
Construction of a new third lane on outbound GWMP from the Key
Bridge/Rosslyn on-ramp to Spout Run Parkway (alternative B) would
facilitate merging and weaving. However, this would also result in the
section of outbound GWMP north of Spout Run Parkway operating just
below capacity.
Construction of new third and fourth lanes between the on-ramp from Key
Bridge/Rosslyn and Spout Run Parkway (alternatives C and D) would
facilitate merging and weaving on this outbound section. The number of
rear-end and side-swipe accidents might be reduced by adding new lanes.
However, the outbound section of GWMP north of Spout Run Parkway
would be at or near capacity under these alternatives.
Construction of a short merge lane on outbound GWMP north of Spout Run
Parkway (alternatives C and D) would facilitate weaving in the critical
section prior to the outbound Spout Run Parkway exit. Evening
peak-hour outbound travel times would be shorter in alternatives B and D
than they are at present throughout the study area. Under alternative C
travel times would be shorter than at present from the Key Bridge
on-ramp to the north end of the study area, but travel times from the
Roosevelt Bridge on-ramp would be longer.
The reconstruction of the Lorcom Lane/Spout Run intersection to allow
left-hand turns (alternatives B, C, and D) would improve access to
Lorcom Lane from Kirkwood (VA 124).
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STUDY AREA TRAFFIC FLOWS
The projected weekday average traffic volumes for each alternative are
presented in tables 19 and 20. The projected traffic volumes during the
morning and evening peak hours are shown in tables 21 and 22. The
figures in tables 21 and 22 are intended to represent future peak-hour
use, but not necessarily the total peak-hour demand. Demand volumes
and use volumes would be the same until they reached the capacity of a
section of roadway or a ramp. The demand volumes could exceed the
capacity, but the use volumes could not, since capacity is, by definition,
the maximum number of vehicles that could use the roadway at any one
time. Wherever demand exceeded capacity, backups would occur. The
situations where this would be expected to happen are explained in the
text for each alternative.
Alternative A
Inbound/Morning Peak Hour. In the absence of traffic signals at the
Lorcom Lane/Spout Run intersection it would remain necessary to close
outbound Spout Run west of Lorcom Lane during the morning peak
period, making it impossible for outbound vehicles to travel directly to
Lee Highway and outbound 1-66.
At the critical junction of the Spout Run entrance to GWMP a police
officer would still direct traffic and allocate the right-of-way. It is
estimated that a maximum of 3,600 vehicles per hour (one vehicle per lane
every two seconds) could pass through the intersection with this type of
traffic control. If inbound GWMP received the right-of-way 80 percent of
the time during the morning peak period, 2,900 vehicles per hour could
pass through the intersection on GWMP and 700 vehicles per hour could
pass through the intersection from inbound Spout Run Parkway. In spite
of the restricted capacities of the roadways, inbound traffic on GWMP
from 1-495 near the Cabin John Bridge and from VA 123 would increase
during the morning peak period, as would traffic on Spout Run Parkway.
The length of the traffic queues north of Spout Run Parkway would
increase from 2.3 miles to 2.4 miles.
The inbound off-ramp to Rosslyn Circle and Key Bridge would remain
closed during the morning peak period; consequently, there would be no
change from current operating conditions.
By 1990, 1,800 vehicles would attempt to use the off-ramp to Roosevelt
Bridge during the morning peak hour, and by 2000 this demand would
have increased to more than 2,000 vehicles. The theoretical capacity of
the off-ramp is 2,000 vehicles per hour. However, because of the lane
configuration of inbound 1-66 onto the Roosevelt Bridge, traffic from the
GWMP off-ramp must merge with through-traffic on inbound 1-66 prior to
the bridge entrance. Consequently, not all of the 1,800 to 2,000 vehicles
attempting to exit GWMP would be able to pass through the junction with
inbound 1-66 during the morning peak hour. Traffic would back up on
the ramp, and drivers attempting to use this ramp would experience
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Table 19: Short-Term (1990) Projections of Weekday Average
Daily Traffic on GWMP/Spout Run Parkway
Existing
Projections for Alternatives
(1984)
A
B
C
D
GWMP from VA 123 to
Spout Run
26,500
28,500
31,000
39,000
39,000
GWMP from Spout Run to off-
ramp to Key Bridge/Rosslyn
35,000
37,500
42,000
50,000
50,000
GWMP from off-ramp to Key
Bridge/Rosslyn to off-ramp
to Roosevelt Bridge
27,500
29,500
34,000
39,000
30,000
GWMP from off-ramp to
Roosevelt Bridge to on-ramp
from US 50
20,000
20,500
25,000
31,500
24,000
Off-ramp to Key Bridge/
Rosslyn
7,500
8,000
8,000
11,000
11,000
Off-ramp to Roosevelt Bridge
7,500
9,000
9,000
8,500
6,500
Spout Run Parkway
Outbound
8,500
9,000
11,000
11,000
11,000
GWMP from on-ramp from
Memorial Circle to on-ramp
from Roosevelt Bridge
20,000
21,500
21,000
24,500
24,500
GWMP from on-ramp from
Roosevelt Bridge to on-ramp
from Key Bridge/Rosslyn
28,000
31,000
31,000
35,000
35,500
GWMP from on-ramp from Key
Bridge/Rosslyn to Spout Run
42,000
46,000
48,000
52,000
52,500
GWMP from Spout Run to
30,500
33,500
36,000
36,000
36,500
VA 123
On-ramp from Roosevelt Bridge
8,000
9,500
10,000
10,500
11,000
On-ramp from Key Bridge/
Rosslyn
14,000
15,000
17,000
17,000
17,000
Spout Run Parkway
11,500
12,500
12,000
16,000
16,000
Source: Existing traffic volumes were derived from data collected by FHWA in
June and July 1984 and rounded to the nearest 500 vehicles per day.
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Table 20: Long-Term (2000) Projections of Weekday Average
Daily Traffic on GWMP/Spout Run Parkway
Existing
Projections for Alternatives
Inbound
(1984)
A
B
C
D
GWMP from VA 123 to Spout
26,500
32,000
35,000
44,000
44,000
Run
GWMP from Spout Run to off-
35,000
42,000
47,000
56,000
56,000
ramp to Key Bridge/Rosslyn
GWMP from off-ramp to Key
27,500
33,000
38,000
43,500
33,500
Bridge/Rosslyn to off-ramp to
Roosevelt Bridge
GWMP from off-ramp to
20,000
21,000
26,000
32,500
25,000
Roosevelt Bridge to on-ramp
from US 50
Off-ramp to Key Bridge/Rosslyn
7,500
9,000
9,000
12,500
12,500
Off-ramp to Roosevelt Bridge
7,500
12,000
12,000
11,000
8,500
Spout Run Parkway
8,500
10,000
12,000
12,000
12,000
Outbound
GWMP from on-ramp from
20,000
24,000
22,000
27,500
27,500
Memorial Circle to on-ramp
from Roosevelt Bridge
GWMP from on-ramp from
28,000
36,000
39,000
41,000
41,000
Roosevelt Bridge to on-ramp
from Key Bridge/Rosslyn
GWMP from on-ramp from Key
42,000
52,000
55,000
57,000
57,000
Bridge/Rosslyn to Spout Run
GWMP from Spout Run to
30,500
38,000
41,500
38,000
38,000
VA 123
On-ramp from Roosevelt Bridge
8,000
12,000
13,000
13,500
13,500
On-ramp from Key Bridge/
14,000
16,000
16,000
16,000
16,000
Rosslyn
Spout Run Parkway
11,500
14,000
13,500
19,000
18,500
Source: Existing traffic volumes were derived from data collected by FHWA
in June and July 1984 and rounded to the nearest 500 vehicles per day.
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Table 21: Short-Term (1990) Projections of Peak-Hour Traffic on
GWMP/Spout Run Parkway
Inbound/Morning Peak Hour
Existing
Projections for Alternatives (vph)
(7:00-8:00)
1984)
A
B
C
D
GWMP from VA 123 to Spout Run
2,750
2,900
2,950
4,000*
4,000*
GWMP from Spout Run to off-
ramp to Key Bridge/Rosslyn
3,450
3,600*
3,750
5,600
5,700
GWMP from off-ramp to Key
Bridge/Rosslyn to off-ramp to
Roosevelt Bridge
3,450
3,600
3,750
3,600
2,800
GWMP from off-ramp to Roosevelt
Bridge to on-ramp from US 50
2,150
1,800
1 , 850
1 , 650
1 , 400
Off-ramp to Key Bridge/Rosslyn
0**
0**
0**
1,250***
1,250***
Off-ramp to Roosevelt Bridge
1,300
1,800
1,900
1,700
1,400
Spout Run Parkway
Outbound Evening Peak Hour
700
700
800
1,600
1,700
(5:00-6:00)
GWMP from on-ramp from
Memorial Circle to on-ramp from
Roosevelt Bridge
1,900
1,700
1,500
1,650
1,650
GWMP from on-ramp from
Roosevelt Bridge to on-ramp from
Key Bridge/Rosslyn
3,000
3,100
3,000
3,300
3,300
GWMP from on-ramp from Key
Bridge/Rosslyn to Spout Run
4,350
4,500*
4,800
5,100
5,100
GWMP from Spout Run to VA 123
3,250
3,350
3,700
3,850
3,850
On-ramp from Roosevelt Bridge
1,100
1,400
1,500
1,650
1,650
On-ramp from Key Bridge/
Rosslyn
1,600
1,800*
1,800*
1,800*
1,800*
Spout Run Parkway
1,100
1,200
1,100
1,250
1,250
Source: Existing traffic volumes were derived from raw traffic count data collected by
FHWA in June and July 1984 and rounded to the nearest 50 vehicles per hour.
* Represents maximum flow possible for lane configuration/traffic control/facility type.
** Closed to traffic 7:00 to 9:00 a.m.
***This figure assumes that GWMP off-ramp traffic is required to merge with
traffic from North Lynn Street prior to crossing Key Bridge.
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Long-Term (2000) Projections of Peak-Hour Traffic on
GWMP/Spout Run Parkway
Inbound Morning Peak Hour
Existing
Projections for Alternatives (vph)
(7:00-8:00)
(1984)
A B C D
GWMP from VA 123 to Spout Run
2,750
2,900
3,150
4,000*
4,000*
GWMP from Spout Run to off-
ramp to Key Bridge/Rosslyn
3,450
3,600*
4,000*
5,700
5,850
GWMP from off-ramp to Key
Bridge/Rosslyn to off-ramp to
Roosevelt Bridge
3,450
3,600
4,000
3,700
2,750
GWMP from off-ramp to Roosevelt
Bridge to on-ramp from US 50
2,150
1,600
2,200
1,700
1,300
Off-ramp to Key Bridge/Rosslyn
0**
0**
0**
1,250***
1,250***
Off-ramp to Roosevelt Bridge
1,300
2,000*
2,000*
2,000*
1,450
Spout Run Parkway
Outbound Evening Peak Hour
700
700
850
1,700
1,850
(5:00-6:00)
GWMP from on-ramp from
Memorial Circle to on-ramp from
Roosevelt Bridge
1,650
1,500
1,700
1,900
GWMP from on-ramp from
Roosevelt Bridge to on-ramp from
Key Bridge/Rosslyn
3,000
3,250
3,250
3,700
3,700
GWMP from on-ramp from Key
Bridge/Rosslyn to Spout Run
4,350
4,500*
5,050
5,500
5,500
GWMP from Spout Run to VA 123
3,250
3,350
3,950
3,950
4,000*
On-ramp from Roosevelt Bridge
1,100
1 , 600
1 , 750
1, 800*
1, 800*
On-ramp from Key Bridge/
Rosslyn
1,600
1,800*
1,800*
1,800*
1,800*
Spout Run Parkway
1,100
Source: Existing traffic volumes were derived from raw traffic count data collected by
FHWA in June and July 1984 and rounded to the nearest 50 vehicles per hour.
*Represents maximum flow possible for lane configuration/traffic control/facility type.
**Closed to traffic 7:00 to 9:00 a.m.
***This figure assumes that GWMP off-ramp traffic is required to merge with
traffic from North Lynn Street prior to crossing Key Bridge.
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lengthy delays. In the year 2000 it would take approximately 23 minutes
to travel from a point on GWMP north of Spout Run to the off-ramp for
Roosevelt Bridge. Furthermore, the projected morning peak-hour demand
for Roosevelt Bridge would exceed the capacity by approximately 1,350
vehicles by the year 2000. Projected demand volumes on the major
inbound approaches to the bridge would be
Vehicles per Hour
1 90
2000
Ramp from GWMP to inbound 1-66
1,800
2,000
Inbound 1-66
2,200
2,300
Ramp from inbound US 50
2,600
3,050
Total
6,600
7,350
In comparison, the theoretical capacity of the bridge (with three lanes in
each direction) would be only 6,000 vph in either direction.
Consequently, it is likely that long queues would form at the bridge and
back up on GWMP for 2.3 miles. Drivers approaching on inbound US 50
would also experience lengthy delays.
Outbound/Evening Peak Hour. By 1990 it is projected that the peak-hour
traffic volume on outbound Roosevelt Bridge would be 5,400 vehicles per
hour. Of that number approximately 1,400 vehicles would exit to the
GWMP on-ramp, 2,000 would take outbound 1-66, and 2,000 would exit
onto outbound US 50. By the year 2000 the demand for outbound
Roosevelt Bridge would be at capacity. Assuming that no capacity
improvements were made to the bridge or to the Constitution Avenue/23rd
Street signalized intersection, the maximum number of vehicles that could
cross the three-lane bridge during the evening peak hour would be
6,000. It is projected that 1,600 vehicles would exit to the GWMP
on-ramp, 2,400 would proceed on outbound 1-66, and 2,000 would exit
onto outbound US 50, as summarized below:
Vehicles per Hour
1990
2000
On-ramp to GWMP
1,400
1,600
Outbound I-66/Rosslyn
2,000
2,400
On-ramp to US 50
2,000
2 000
Total
5,400
66, 0000
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In the year 2000 it would take 8.5 minutes to travel from the on-ramp
from Roosevelt Bridge to a point on GWMP north of Spout Run. The
demand for the on-ramp from Key Bridge/Rosslyn would exceed the
capacity of the ramp, causing backups to occur on the bridge. A
maximum of 1,800 vehicles per hour could enter GWMP by way of this
single-lane on-ramp.
Existing counts indicate that a maximum volume of 4,500 vph could travel
through the section of outbound GWMP between Key Bridge and Spout
Run in the absence of any structural changes. The projected evening
peak-hour traffic would exceed the capacity of this section by
approximately 550 vph by the year 2000. The projected evening
peak-hour volumes for the approaches to this section of GWMP would be
Vehicles per Hour
1990 2000
Outbound GWMP 3,100 3,250
On-ramp from Key Bridge/Rosslyn 1,800 1,800
Total 4,900 5,050
This excess demand would result in queues on the on-ramp that would not
dissipate until after the evening peak hour. In the year 2000 it would
take 4.4 minutes to travel from the Key Bridge on-ramp to a point on
GWMP north of Spout Run. Beyond this critical bottleneck, it is
projected that 1,150 vehicles would exit onto Spout Run Parkway during
the evening peak hour and that 3,350 vehicles would continue on GWMP
by the year 2000.
Alternative B
Inbound/Morning Peak Hour. Similar to alternative A, it would remain
necessary to close outbound Spout Run west of Lorcom Lane during the
morning peak period, thus restricting outbound traffic flow to Lee
Highway and 1-66.
The provision of an acceleration lane of adequate length to allow traffic
on Spout Run Parkway to merge onto inbound GWMP would eliminate the
need for a police officer to direct traffic at this critical junction during
the morning peak period. The projected inflows to this critical junction
would be
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Vehicles per Hour
1990
2000
Spout Run Parkway
800
850
Inbound GWMP
2,950
3,150
Total
3,750
4,000
The projected demand volume would reach the theoretical capacity of a
two-lane directional facility by the year 2000. Any slight disruption to
the traffic flow, such as an accident, would quickly create congestion and
cause lengthy motorist delays. Traffic queues would not be expected on
GWMP north of Spout Run Parkway; however, the queues on Spout Run
Parkway would increase from 0.5 mile to 1.1 miles, which would extend
beyond Lee Highway.
The ramp to Key Bridge would remain closed during the morning peak
hour. Consequently, peak-hour traffic flow would not be affected at this
location.
Similar to alternative A, congestion problems would still result at the
junction of 1-66 and the GWMP off-ramp to Roosevelt Bridge and at the
junction of 1-66 and the ramp from inbound US 50 because of inadequate
capacity on the bridge. Queue lengths would be 2.3 miles, the same as
in alternative A, at this location. In the year 2000 it would take 20
minutes to travel from a point on GWMP north of Spout Run to the
Roosevelt Bridge off-ramp.
Outbound/Evening Peak Hour. The projected evening peak-hour demand
for the outbound Roosevelt Bridge would exceed its capacity by the year
2000. As in alternative A, the maximum number of vehicles that could
cross the bridge would be 6,000. The lengthened acceleration lane for
the GWMP on-ramp from Roosevelt Bridge would facilitate the merge. It
is projected that the number of vehicles using this ramp during the
evening peak hour would increase to 1,500 vph by 1990 and 1,750 vph by
2000. In the year 2000 it would take 6.5 minutes to travel from the
on-ramp from Roosevelt Bridge to a point on GWMP north of Spout Run
Parkway.
Similar to alternative A, the projected demand for the on-ramp from Key
Bridge/Rosslyn would exceed the capacity of the ramp, causing backups
on the bridge. The projected evening peak-hour volumes on the section
of GWMP between the on-ramp from Key Bridge/Rosslyn and Spout Run
Parkway would be
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Vehicles per Hour
1990 2000
Outbound GWMP 3,000 31250
On-ramp from Key Bridge/Rosslyn 1,800 1,800
Total 4,800 5,050
In the year 2000 it would take 2.6 minutes to travel from the on-ramp
from Key Bridge to a point on GWMP north of Spout Run Parkway.
The evening peak-hour traffic exiting onto Spout Run Parkway would be
1,100 vph in both 1990 and 2000.
Alternative C
Inbound/Morning Peak Hour. The installation of traffic signals at the
intersection of Lorcom Lane and Spout Run Parkway would eliminate the
need to close outbound Spout Run west of Lorcom Lane during the
morning peak period. Traffic signals would safely accommodate all
vehicles turning at or proceeding through this intersection 24 hours a
day, including outbound vehicles traveling directly to Lee Highway and
outbound 1-66 during the morning peak period. Elimination of the
traditional free-flowing movement from Lorcom Lane to inbound Spout Run
Parkway during the morning peak hours would create traffic queues on
Lorcom Lane. No queues would occur on Spout Run Parkway. The
periodic delays caused by signal phasing might be considered an
inconvenience by local users, and the cars waiting at the intersection
might be a nuisance to residents along Lorcom Lane, depending on the
length of the queues.
Because of the additional capacity created by the new third inbound lane
between Spout Run Parkway and the reconstructed and reopened off-ramp
to Key Bridge, it is projected that the morning peak-hour volume on
Spout Run Parkway would increase to 1,600 vph by 1990 and to 1,700 vph
by 2000. The peak hour volumes on the inbound section of GWMP
between Spout Run and Key Bridge would increase to 5,600 vehicles by
the year 1990, and to 5,700 vehicles by the year 2000, as shown below:
Vehicles per Hour
1990
2000
Spout Run Parkway
1,600
1,700
Inbound GWMP
4,000
4,000
Total
5,600
5,700
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These volumes would be near the theoretical 6,000 vph capacity of a
three-lane roadway. The projected peak-hour volumes for the off-ramp to
Key Bridge would exceed the capacity by 1990, causing backups on
GWMP. The capacity of the ramp would be 1,250 so long as GWMP
off-ramp traffic was required to merge with traffic from North Lynn
Street prior to crossing Key Bridge. A theoretical maximum of 2,000 vph
could use the reconstructed and improved ramp if North Lynn Street was
reduced to two lanes prior to the ramp junction and if the ramp traffic
was unimpeded at the junction (that is, if it could cross Key Bridge in a
continuous lane). Traffic queues up to 2.8 miles might develop on GWMP.
In the year 2000 it would take 9.8 minutes to travel from a point on
GWMP north of Spout Run Parkway to the Key Bridge off-ramp.
The projected morning peak-hour demand for the two-lane section of
GWMP between Key and Roosevelt bridges would be 3,600 by 1990 and
3,700 by the year 2000. In the year 2000 it would take 10.9 minutes to
travel from a point on GWMP north of Spout Run Parkway to the
Roosevelt Bridge off-ramp.
As with alternatives A and B, congestion would still occur at the
junctions of 1-66 with the GWMP off-ramp to Roosevelt Bridge and with
the ramp from inbound US 50. By the year 2000 the projected traffic
volumes exiting the off-ramp to Roosevelt Bridge would be 2,000 vph. Of
this, it is projected that only 500 vph would desire to use the new ramp
to outbound US 50 and gain access to Rosslyn via this route. The new
exit ramp to US 50 might attract some commuters to the parkway who
currently use other routes through Arlington. This would potentially
reduce the congestion at Rosslyn Circle during the morning rush hours
compared to alternatives B and D. Also, routing traffic into Rosslyn by
way of US 50 would provide better access to the larger commercial district
of Arlington.
Outbound/Evening Peak Hour. As with alternative B the projected
evening peak-hour demand on the outbound Roosevelt Bridge would
exceed the capacity of the bridge by the year 2000. The lengthened
acceleration lane for the GWMP on-ramp from Roosevelt Bridge would
facilitate the merge. During the evening peak hour, 1,650 vehicles would
attempt to enter GWMP from Roosevelt Bridge by 1990 and 1,800 vehicles
would attempt to use the on-ramp by the year 2000. In the year 2000 it
would take 7.4 minutes to travel from the on-ramp from Roosevelt Bridge
to a point on GWMP north of Spout Run Parkway.
The projected demand for the on-ramp from Key Bridge/Rosslyn would
exceed the capacity of the ramp, causing traffic backups on the bridge.
A maximum of 1,800 vph could enter GWMP from this ramp during the
evening peak hour. The added third and fourth lanes on outbound GWMP
from the Key Bridge/Rosslyn on-ramp to the Spout Run exit would allow
additional space and time for merging and changing lanes, and they would
allow the on-ramp traffic desiring to exit at Spout Run to do so without
weaving.
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The peak-hour volumes on the section of outbound GWMP between the
on-ramp from Key Bridge/Rosslyn and the Spout Run exit would be
Vehicles per Hour
1990 2000
Outbound GWMP 3,300 3,700
On-ramp from Key Bridge/Rosslyn 1,800 1,800
Tota 1 5,100 5,500
In the year 2000 it would take 2.6 minutes to travel from the on-ramp
from Key Bridge to a point on GWMP north of Spout Run Parkway. The
taper of three lanes to two just beyond the Spout Run exit would allow
vehicles in the left-hand lane to stay on GWMP and to merge into the
through-lanes beyond the Spout Run exit. The projected volume on the
section of GWMP north of the Spout Run exit would be very close to the
theoretical 4,000 vph capacity of that two-lane section.
Alternative D
Inbound/Morning Peak Hour. As with alternative C, the installation of
traffic signals at the intersection of Lorcom Lane and Spout Run Parkway
would eliminate the need to close outbound Spout Run west of Lorcom
Lane during the morning peak period, but it would cause traffic queues
on Lorcom Lane. Traffic signals would safely accommodate all vehicles
turning at or proceeding through this intersection 24 hours a day. No
queues would occur on Spout Run Parkway.
The construction of a third inbound lane from Spout Run Parkway to the
off-ramp to the Roosevelt Bridge, the opening of a reconstructed off-ramp
to Key Bridge, and the construction of a new off-ramp to Rosslyn and
Fort Myer Drive would create a projected demand for inbound GWMP north
of the Spout Run Parkway intersection that would exceed the capacity of
the roadway by the year 1990. The maximum number of vehicles that
could travel that section of roadway would be 4,000. Thus, the projected
peak-hour inflows to the critical intersection between GWMP and Spout
Run Parkway would be
Vehicles per Hour
1990
2000
Spout Run Parkway
1,700
1,850
Inbound GWMP
4,000
4,000
Total
5,700
5,850
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These volumes would be near the theoretical 6,000 vph capacity of a
three-lane roadway.
It is projected that 900 vehicles would exit inbound GWMP onto the new
ramp to Rosslyn and Fort Myer Drive during the morning peak hour in
1990 and that 1,100 vehicles would use that route in 2000. The
construction of a new off-ramp into Rosslyn Circle would eliminate the
Rosslyn Circle entrance into the Key Bridge Marriott and approximately 40
of the motel parking spaces. This would result in some confusion and
inconvenience for customers who have traditionally used the circle
entrance.
The demand for the reconstructed off-ramp to Key Bridge would exceed
the capacity of a one-lane ramp even if there was an exclusive lane to
accommodate this ramp traffic at the junction with Lynn Street. Not all
of the morning peak-hour traffic arriving at the Key Bridge could be
processed at the opposite end of the bridge during the morning peak
hour. Traffic queues of 2.0 miles would occur on GWMP. In the year
2000 it would take 5.8 minutes to travel from a point on GWMP north of
Spout Run Parkway to the Key Bridge off-ramp.
The projected morning peak-hour volumes exiting at the GWMP off-ramp to
the Roosevelt Bridge would be 1,400 vph in 1990 and 1,450 vph in 2000.
These volumes would be considerably less than the projected volumes on
this ramp for alternatives A, B, and C, because a larger proportion of
the total traffic accommodated on GWMP would exit at Key Bridge and
Rosslyn. In the year 2000 it would take 6.1 minutes to travel from a
point on GWMP north of Spout Run Parkway to the Roosevelt Bridge
off-ramp.
Outbound Evening Peak Hour. As with alternatives B and C the evening
peak-hour demand would exceed the capacity on outbound Roosevelt
Bridge by the year 2000. Of the projected 6,000 vehicles crossing the
bridge during the evening peak hour, approximately 1,650 would exit at
the GWMP on-ramp in 1990 and 1,800 would use the ramp by the year
2000. Because the additional third lane would begin at this location, the
vehicles entering GWMP would not have to yield and merge. In the year
2000 it would take 4.0 minutes to travel from the on-ramp from Roosevelt
Bridge to a point on GWMP north of Spout Run Parkway.
As with alternatives A through C, the projected demands on outbound
Key Bridge and on the on-ramp to GWMP would exceed the capacities of
those facilities. A maximum of only 1,800 vph could enter GWMP from
this ramp. The resulting evening peak-hour volumes on the critical
outbound link of GWMP between the on-ramp from Key Bridge/Rosslyn and
the Spout Run exit would be 5,100 vph in 1990 and 5,500 vph in 2000,
the same as in alternative C. The added third and fourth lanes on
outbound GWMP from the Key Bridge/Rosslyn on-ramp to the Spout Run
exit would allow additional space and time for merging and changing
lanes, and they would allow the on-ramp traffic desiring to exit at Spout
Run to do so without weaving. In the year 2000 it would take 2.6
minutes to travel from the on-ramp from Key Bridge to a point on GWMP
north of Spout Run Parkway.
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The taper of three lanes to two on GWMP beyond the Spout Run exit
would allow vehicles in the left-hand lane to stay on GWMP and to merge
into the through-lanes beyond the Spout Run exit. By the year 2000,
the evening peak-hour traffic on GWMP north of Spout Run Parkway
would nearly reach the theoretical capacity of this two-lane outbound
section.
The projected evening peak-hour volume on outbound Spout Run Parkway
would be 1,250 in 1990 and 1,500 in 2000.
PROJECTED LEVELS OF SERVICE
Tables 23 and 24 present the projected morning and evening peak-hour
levels of service* for each alternative. During the morning peak hour,
the level of service would be very low on the off-ramp to Key
Bridge/Rosslyn (if open) and in the vicinity of the off-ramp to Roosevelt
Bridge, regardless of which alternative was implemented. The level of
service would be improved at the junction of inbound GWMP and the Spout
Run Parkway under alternative C, but the junction would remain capacity
deficient under alternatives A, B, and D.
During the evening peak hours, the level of service would remain low for
merging traffic under all of the alternatives at the junction of outbound
GWMP and the on-ramp from Roosevelt Bridge and for all traffic at the
intersection of Fort Myer Drive and the on-ramp for outbound GWMP.
Actions in alternative D, particularly, and to a lesser extent in
alternative C would improve the level of service on outbound GWMP
between Key Bridge and Spout Run.
ACCIDENTS
Table 25 lists the relative accident potentials for each alternative. It is
impossible to quantify the reduction in accidents that might occur from
roadway improvements, but specific actions to improve the road surface,
provide drivers with better information, reduce congestion, improve sight
distances, and improve roadway geometrics would potentially reduce the
number of accidents. Overall, roadway improvements would be expected
to reduce accident-related injuries and property damage. Lower accident
rates would also mean lower costs for vehicle repairs, medical services,
and insurance rates.
In all alternatives, accidents would potentially be reduced at most of the
locations listed in table 25 as a result of new reflective markings,
guardrails, signing, and skid-resistant surfacing. The potential for
accidents would additionally be reduced at specific locations as described
below.
* Levels of service are described in the "Description of the Environment."
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Table 23: Projected Morning Peak-Hour Levels of Service, 1990 and 2000
1984
Existing
1990
Alternative
2000
Alternative
Route Segment
Network
A
B
C
D
A
B
C
D
Inbound
Lorcom Lane/Spout Run
intersection
Left turn from Lorcom Lane
Total traffic
Junction of Spout Run Parkway
and GWMP
Total traffic
Merging traffic
Junction of GWMP and off-ramp
to Key Bridge/Rosslyn
Diverging traffic
Total traffic
Off-ramp to Key Bridge/Rosslyn
Intersection of off-ramp from
inbound GWMP and Lynn Street
Crossing traffic from ramp
Right-turning traffic from ramp
Off-ramp to Roosevelt Bridge/
inbound 1-66
Junction of off-ramp from
inbound GWMP and inbound 1-66
Merging traffic
Total traffic
Outbound
Al
-
E2
-
3
-
D1
-3
3
-3
-
F5
E
D
Al
-
F2
-
3
-
D1
_3
-3
3
-
F
F
F
Al
-
E
E
3
_1
D1
_3
3
3
-
F
F
F
B
D
D
E
D
F
3
E
F
F
F
C
D
D
E
D
F
4
E
E
F
F
Al
-
F
-
3
-
D1
_3
4
-3
F
F
F
Al
-
E
E
3
-
E
_3
3
-
-3
F
F
F
C
D
D
E
D
F
4
-
E
F
F
F
D
E
E
E
E
F
4
-
E
E
F
F
Junction of on-ramp from
Roosevelt Bridge and outbound
GWMP
Merging traffic
B
B
B
B
A
B
B
B
A
Total traffic
A
A
A
A
A
B
B
B
A
Intersection of Fort Myer Drive
and on-ramp to outbound GWMP
A
B
B
B
C
B
B
C
C
Outbound GWMP from on-ramp
from Key Bridge/Rosslyn to
Spout Run
Merging traffic
C
C
A
A
B
C
B
A
B
Diverging traffic
B
B
A
A
A
B
A
A
A
Total traffic
B
B
A
A
A
B
B
A
A
1. Due to traffic control measures, this maneuver is unimpeded.
2. Due to traffic control measures, this intersection is treated as a two-phase signalized
intersection.
3. Due to traffic control measures, traffic is not permitted on the ramp.
4. Movement would be prohibited.
5. Traffic on ramp is typically restricted during. morning peak period due to traffic conditions
at junction with 1-66 and Roosevelt Bridge. By definition, level of service is F.
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Table 24: Projected Evening Peak-Hour Levels of Service. 1990 and 2000
1984
Existing
Network
Inbound
Lorcom Lane/Spout Run intersection
Left turn from Lorcom Lane E
Total traffic -
Junction of Spout Run Parkway
and inbound GWMP
Total traffic B
Merging traffic -
Junction of inbound GWMP and
off-ramp to Key Bridge/Rosslyn
Diverging traffic B
Total traffic B
Off-ramp to Key Bridge/Rosslyn D1
Intersection of off-ramp from
inbound GWMP and Lynn Street
Crossing traffic from ramp E
Right-turning traffic from ramp D
Off-ramp to Roosevelt Bridge/
inbound 1-66 B
Junction of off-ramp from
inbound GWMP and inbound 1-66
Merging traffic B
Total traffic A
Outbound
Junction of on-ramp from Roosevelt
Bridge and outbound GWMP
Merging traffic E
Total traffic D
Intersection of Fort Myer Drive
and the GWMP on-ramp D
Outbound GWMP from on-ramp
from Key Bridge/Rosslyn to
Spout Run
Weaving traffic F
Merging traffic F
Diverging traffic F
Nonweaving traffic F
1990
Alternative
2000
Alternative
A
B
C
D
A
B
C
D
F
E
-
-
-
-
A
A
C
C
B
B
C
C
B
B
-
C
A
A
-
C
A
A
B
C
B
C
C
D
B
C
C
C
B
B
C
C
B
B
D
B
A
A
D1
C
B
B
F
_2
_2
_2
F
-2
- 2
2
-
E
B
B
B
F
B
B
B
B
B
C
B
B
B
D
B
C
C
C
D
D
D
D
D
C
C
C
C
C
C
C
C
E
E
E
D
E
E
E
E
D
D
D
B
D
D
E
C
E
E
E
E
E
E
E
E
F
E
C
C
F
F
D
C
F
-
-
-
F
-
-
F
-
-
-
F
-
-
F
E
C
D
F
F
D
D
1. Low level of service is caused by ramp geometrics and not volume.
2. Movement would be prohibited.
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Right-angle accidents between vehicles traveling outbound on Spout Run
Parkway and vehicles turning left from Lorcom Lane onto inbound Spout
Run should be reduced by the signalization of the Lorcom Lane/Spout Run
Parkway intersection (alternatives C and D).
Because these alternatives would facilitate free-flow traffic conditions at
the merge, the rear-end accidents on inbound GWMP near the junction
with Spout Run Parkway should be reduced by the addition of a longer
merge lane (alternative B) or a third continuous lane (alternatives C and
D) for traffic entering GWMP from Spout Run Parkway. In alternatives C
and D, the opening of the existing off-ramp to Key Bridge during the
peak morning hours would result in backups on GWMP and stop-and-go
traffic trying to use the ramp. As a result, rear-end and run-off-the-
road accidents would potentially be more numerous than in alternative B.
Rear-end and run-off-the-road accidents at the off-ramp to Key
Bridge/Rosslyn should be reduced by ramp improvements (alternative B).
Accidents should be further reduced by providing alternative access to
Rosslyn by way of a new ramp connecting to US 50 (alternative C).
Even with this alternate access to Rosslyn, however, the morning
peak-hour traffic trying to exit to Key Bridge would cause queues and
stop-and-go traffic on this section of GWMP, so there would be little
potential for improvement in accident rates during the morning rush
hours. If a separate ramp for Rosslyn traffic exited GWMP near the Key
Bridge exit (as would occur in alternative D), the potential for accidents
would probably be higher than it would be if there was greater separation
between the ramps (as would occur in alternative C).
Right-angle and sideswipe accidents at the intersection of the Key
Bridge/Rosslyn off-ramp and North Lynn Street should be reduced by
improvements to the ramp and to the traffic flow in Rosslyn Circle
(alternatives B, C, and D). No right-angle and sideswipe accidents
currently occur at this intersection during the morning rush hours
because the ramp is closed between 7:00 and 9:00 a.m.
Rear-end accidents at the junction of outbound GWMP and the on-ramp
from Roosevelt Bridge should be reduced by improved access to the
Theodore Roosevelt Island parking lot (alternatives B, C, and D), a
longer merge lane at the end of the ramp (alternatives B and C), and a
new third continuous lane for merging traffic (alternative D).
Rear-end and sideswipe accidents at the junction of outbound GWMP and
the on-ramp from Key Bridge/Rosslyn should be reduced by actions that
would allow drivers more space for merging and changing lanes through
this critical segment of the parkway. This would be accomplished by
adding a new third lane (alternative B) or third and fourth lanes
(alternatives C and D) to the section of outbound GWMP between Key
Bridge and Spout Run. The accident potential would be lower under
alternatives C and D because of the greater maneuvering width for
merging and weaving provided by four lanes compared to three.
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Existing
Conditions*
Frequent number of
right-angle accidents
Reduction in right- Same as C
angle collisions
Inbound
Lorcom Lane and
Spout Run Parkway
Spout Run Parkway
and inbound GWMP
'GWMP between Spout
Run Parkway and off-
ramp to Key Bridge
Off-ramp to Key
Bridge/Rosslyn
Key Bridge off-ramp
and Lynn Street
Outbound
5n-ramp from
Roosevelt Bridge
On-ramp from Key
Bridge/Rosslyn at Fort
Myer Drive
GWMP at on-ramp
from Key Bridge/
Rosslyn
Frequent number of
rear-end accidents
Frequent number of
rear-end and run-off-
the-road accidents
Frequent number of
rear-end and run-off-
the-road accidents
Frequent number of
right-angle and side-
swipe accidents
Frequent number of
rear-end accidents
Frequent number of
rear-end accidents
Frequent number of
rear-end and side-
swipe accidents
Frequent number of
run-off-the-road
accidents
Minor reduction in Same as A
accidents as a result of
resurfacing and reha-
bilitation
Minor reduction in Some reduction in rear-
accidents as a result of end accidents over A
resurfacing and reha-
bilitation
Minor reduction in Some reduction in all
accidents as a result of accidents over A
resurfacing and reha-
bilitation
Minor reduction in Some reduction in all
accidents as a result of accidents over A
resurfacing and reha-
bilitation
Same as existing con- Some reduction in all
ditions accidents over A
Minor reduction in Some reduction in rear-
accidents as a result of end accidents over A
resurfacing and reha-
bilitation
Same as existing con- Some reduction in all
ditions accidents over A
Minor reduction in Some reduction in all
accidents as a result of accidents over A
resurfacing and reha-
bilitation
Minor reduction in Same as A
accidents as a result of
resurfacing and reha-
bilitation
Additional minor re- Same as A
duction in accidents
over B except during
the peak hour
Additional minor re- Same as C
duction in accidents
over B except during
the peak hour
Same as B except Same as C
during the peak hour
Additional minor re- Same as C
duction in accidents
over B
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Run-off-the-road accidents on Spout Run Parkway should be reduced by
the improvement of grades and curves (all alternatives).
REGIONAL IMPACTS
When examined from the perspective of the entire Washington metropolitan
area, the five alternatives would have an almost negligible impact on
regional vehicle miles of travel and regional vehicle hours of travel. An
estimated 10 million vehicle miles of travel would occur during a peak
hour under each alternative. The maximum difference in regional miles of
travel between any of the alternatives would be less than 0.05 percent.
In regional miles, an estimated 300,000 vehicle hours of travel would
occur during a peak hour under each alternative.
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CONSULTATION AND COORDINATION
RELATED STUDIES BY OTHER AGENCIES
Alterations to GWMP between Spout Run Parkway and Roosevelt Bridge
have been considered on a number of occasions, and several technical
studies and plans have been prepared. In 1967 the U.S. Bureau of
Public Roads (now the Federal Highway Administration) prepared plans
for widening, paving, and ramp relocation (project 1A31). In 1972 the
FHWA followed up on that project with a report and plan containing six
alternatives. In 1978 the FHWA prepared a two-volume accident report on
the parkway. Changes to the Lorcom Lane/Spout Run Parkway
intersection have also been studied. In 1980 the Arlington County
Department of Public Works completed an assessment of alternatives for
Lorcom Lane between North Edgewood Street and Spout Run Parkway.
This study assessed the traffic and accidents at the intersection, then
analyzed various alternatives and made recommendations for modifying the
intersection. Selected information and proposals from these previous
studies were incorporated into this environmental impact statement.
CONSULTATION AND COORDINATION IN THE PREPARATION OF THE
DEIS
Work on the NPS study began in January 1984. An informational meeting
was held in Arlington, Virginia, in February to brief various area
jurisdictions regarding the study and to hear their ideas and concerns.
A notice of intent to prepare an environmental impact statement was
published in the Federal Register on March 14, 1984.
The Federal Highway Administration, the Virginia Department of Highways
and Transportation, the Arlington County Department of Public Works,
and the District of Columbia Department of Public Works were invited to
participate as coordinating agencies in the development of the EIS. All
four agencies provided input to the study area issues and the preliminary
alternatives, both during project scoping and through the production of
the draft EIS. The Federal Highway Administration, Eastern Direct
Federal Division, Arlington, Virginia, provided cross sections and cost
estimates for each EIS alternative, furnished data collected from periodic
traffic counts within the study segment, and developed a contour map of
the Little River shoreline. The Virginia Department of Highways and
Transportation and the District of Columbia Department of Public Works
made specific recommendations regarding the study area. The Virginia
Department of Highways and Transportation generally favored alternative
D, full-time access to Key Bridge, and possible establishment of HOV
restrictions on the GWMP off-ramp to Roosevelt Bridge. The District of
Columbia Department of Public Works recommended adding a third lane
outbound between Roosevelt Bridge and Spout Run, reconfiguration of the
GWMP off-ramp to Key Bridge to permit morning peak-hour access to
Rosslyn, improvement to Rosslyn Circle, and adding a third lane inbound
between Spout Run and Key Bridge.
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Other agencies and organizations that were involved in the study included
the National Capital Planning Commission, which assisted in the
distribution of an informational brochure and commented on the
alternatives.
Bellomo-McGee, Inc., traffic engineering consultants from Vienna,
Virginia, were contracted to provide traffic forecasts for each alternative,
traffic safety recommendations, an analysis of air quality and noise, and
an analysis of traffic weaving patterns outbound between Key Bridge and
Spout Run Parkway.
The Washington Metropolitan Area Council of Governments was contracted
to provide socioeconomic data and travel and employment assumptions for
the region using the latest and most up-to-date "Round 3" forecasts.
These forecasts are based on 1980 census data and are composited by
information compiled by each member COG jurisdiction.
The U.S. Fish and Wildlife Service was consulted to determine the status
of endangered or threatened wildlife and plant species within the
parkway. They were also consulted to determine the impacts of
construction on the Potomac River wetlands.
PUBLIC INVOLVEMENT
An informational brochure was prepared in April 1984, and more than
2,000 copies were distributed to the public. Between April 25 and May 2
public scoping meetings were held in McLean, Reston, Arlington,
Bethesda, and the District of Columbia. A total of 65 persons attended
the five meetings. Most of those who attended represented either
themselves, a neighborhood association, or a conservation group.
Following the introductory presentations by the National Park Service, the
public broke into small groups to discuss and record their concerns. In
addition to attending public meetings, the public was invited to send in
comments using the mail-back comment sheet provided in the brochure.
The comment period was from April 7 to July 7, 1984. During that period
the National Park Service received 69 written responses: 43 responses
from individuals, 13 from government offices, 11 from neighborhood
associations, and 2 from vanpool groups. Approximately 80 percent of
these responses contained specific and often very substantive comments.
The written comments reflected many of the same concerns and ideas
recorded at the public meetings, but generally went into greater detail
about specific options to resolve the problems. Both public meeting and
written comments are summarized below.
General: One observation expressed repeatedly by individuals was
that traffic volumes on GWMP had declined since 1-66 had opened and
that congestion was not a major problem, especially compared to the
traffic congestion on other major roads. Lower inbound volumes
were particularly noted. The people who made these comments were
cautious about supporting any major construction changes. Those
who did support construction alternatives generally supported the
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minimum changes necessary to resolve problems in specific locations
in the study area (see the discussion under "Construction Options").
HOV/Ridesharing: In general, HOV restrictions were strongly
opposed for the following reasons:
The irregular work schedules of many commuters prevent them
from carpooling.
Traffic shifts would further congest other roads (both
neighborhood and major arteries).
HOV restrictions would be confusing to tourists.
The access into the District provided by GWMP has been a
major incentive for some of the individuals and companies who
have located in Fairfax and Montgomery counties.
The mass transit systems are inadequate in parts of Fairfax and
Montgomery counties.
There would be no alternative routes for non-carpoolers because
of the HOV restrictions on 1-66.
Voluntary ridesharing, on the other hand, was considered a very
acceptable alternative by the majority. Several suggestions were
made on how to accomplish this:
Advertise vanpool information along the parkway (783-Pool).
Provide park-and-ride facilities near access points along the
parkway.
Bring the subway out to Tyson's Corner and Dulles Airport.
Increase the number of buses, bus stops, and frequency of bus
service in the suburbs.
Spout Run Parkway: Several respondents opposed the closure of
Spout Run Parkway because they felt it gave undue preference to
Fairfax and Montgomery county commuters at the expense of
Arlington residents. Some felt that by eliminating Spout Run traffic
even more commuters from the outlying suburbs would be encouraged
to use GWMP and eventually congestion would return. Several
persons voiced their concern that diverted Spout Run traffic would
cause additional congestion and safety problems on Lee Highway.
Several Arlington residents also were strongly against installing
traffic lights at Lorcom Lane or GWMP. Another suggestion was to
remove the U.S. Park Police officer and allow the inbound left lane
of GWMP to keep moving while using the right lane as a merge area
for Spout Run traffic.
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Other Traffic Management Ideas and Comments: The following is a
range of other traffic management ideas expressed by various
respondents:
Encourage government and nongovernment offices to stagger
work hours further to spread out the commuting period.
Improve mass transit alternatives.
Impose a commuter use-fee during rush hour periods. This
might involve setting up collection points or requiring the
purchase of commuter stickers.
Establish "queue jumpers" for vehicles with two or more
occupants, especially at constrictive points such as Spout Run
and Lorcom Lane.
Close GWMP inbound at VA 123 in the morning.
Close the Key Bridge ramp during the evening rush hour.
Decrease HOV-3 to HOV-2 on 1-66.
Remove HOV restrictions from 1-66 and 395.
Study peak-hour reversible lanes (all lanes one-way or one lane
switched in direction of rush hour traffic).
Improve Canal Road and MacArthur Boulevard to encourage
traffic to stay on the Maryland side of the river.
Construction Options: The responses received concerning
construction options were mixed. However, certain concerns were
consistently raised during the public meetings regarding construction
alternatives. They focused on the effectiveness of construction
alternatives within the context of regional problems. Specifically,
several individuals were concerned that widening the parkway might
only temporarily ease traffic congestion and actually create more
traffic demand. Some felt that the limitations of the bridges and the
District arterials would continue to create traffic bottlenecks which
would negate any benefits from road widening. One participant
voiced his opinion that traffic problems would always exist because
the metropolitan area continues to grow and generate more traffic.
Many people, both in writing and at the meetings, supported some
level of construction. The construction options recommended by
participants focused primarily on improving specific problem areas.
Roadway resurfacing was commonly supported. Also, it was
recommended that the double weave problem on outbound GWMP
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between the Key Bridge on-ramp and the Spout Run exit be solved.
One person recommended widening the Key Bridge on-ramp.
Another suggestion was to improve the Roosevelt Bridge on-ramp to
provide enough room for traffic to merge. For inbound morning
traffic, one participant suggested lengthening the off-ramp to the
Roosevelt Bridge. Additional construction alternatives suggested by
individuals included adding a lane inbound between Spout Run
Parkway and Roosevelt Bridge and widening Roosevelt Bridge.
Safety: The majority of participants endorsed the concept of
enhancing the safety of the roadway. The following specific options
were suggested:
Provide reflective striping on both parkways.
Groove the roadway for better traction.
Lower the speed limit.
Improve speed zone enforcement.
Improve the roadbed surface.
Improve lighting along the parkway.
Provide road shoulders.
The Environment: The majority of respondents expressed concern
for the environmental and scenic qualities of GWMP. In general they
all wanted to maintain the aesthetic qualities of the parkway
regardless of the alternative chosen. The following concerns were
expressed:
The parkway is one of the most beautiful entrances to a capital
city in the world.
The beauty of the parkway is important to the quality of life in
the Washington area.
The beauty of the parkway is more valuable than its use as a
commuter road.
Widening the parkway would conflict with air quality control
efforts in this region.
The beauty of the Potomac River waterfront and palisades would
be damaged by widening the parkway.
Widening the parkway in one section would open the door
someday to widening the rest of the parkway.
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The natural resources of the parkway, such as the trees,
streams, and wildlife habitat, should be preserved.
The vistas of the river and the monuments should be
maintained.
The waterfront values and safe access to Theodore Roosevelt
Island should be protected.
Recreation: Those who commented on recreation options generally
expressed a desire to see better pedestrian and bicycle access to the
riverfront from Arlington.
A complete copy of all written and verbal comments is available at the
parkway headquarters building at Turkey Run, Virginia.
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AGENCIES AND ORGANIZATIONS TO WHOM COPIES OF THE DEIS HAVE
BEEN SENT
Federal Agencies
Advisory Council on Historic Preservation
Central Intelligence Agency
Commission of Fine Arts
Department of Agriculture
Soil Conservation Service
Department of the Army
Corps of Engineers
Department of the Interior
Fish and Wildlife Service
Department of Transportation
Federal Highway Administration
Environmental Protection Agency
General Services Administration
Federal Emergency Management Agency
National Capital Planning Commission
State Agencies
Maryland State Clearinghouse
Department of Natural Resources
Department of State Planning
Department of Transportation
Historic Preservation Officer
National Capital Park and Planning Commission
Virginia State Clearinghouse
Air Pollution Control Board
Council on the Environment
Department of Highways and Transportation
Division of Parks and Recreation
Historic Landmarks Commission
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Local Agencies
Arlington County
County Board
Department of Public Works
Environmental Improvement Commission
Parks Division
Planning Division
Transportation Commission
Alexandria
Office of Community Development
Office of Transportation and Environmental Services
Fairfax County
County Executive
Office of Comprehensive Planning
Office of Transportation
Metropolitan Washington Council of Governments
Montgomery County
County Council
Office of Management and Budget
Planning Board
Northern Virginia Planning District Commission
Northern Virginia Transportation Commission
Washington, D.C.
City Administrator
Department of Public Works
Department of Recreation
Historic Preservation Officer
Mayor's Office
Office of the Budget
Office of Planning
Washington Metropolitan Area Transit Authority
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APPENDIX A: CONSTRUCTION COST ESTIMATES
The following cost estimates are in 1985 dollars and include the costs of
preliminary engineering and construction engineering and supervision.
Annual maintenance costs are not included.
To maintain traffic flow during construction, it may be necessary to
construct at night. This would result in an approximate 30 percent
increase in cost estimates regardless of the alternative.
Alternative A
Removal of curb and pavement (67,000 sq yd)
Pavement (67,000 sq yd)
Curb (55,000 lin ft)
Drainage (LS)
Traffic control (LS)
Stabilize Spout Run embankment (LS)
Mobilization (LS)
Miscellaneous (CS)
Landscaping (LS)
Total
Alternative B
Removal of curb and pavement (67,000 sq yd)
Earthwork (18,000 cu yd)
Pavement (78,000 sq yd)
Curb (55,000 lin ft)
Retaining walls (31,000 sq ft)
Drainage (LS)
Traffic control (LS)
Bridge (LS)
TRI parking area* (3,000 sq yd)
Stabilize Spout Run embankments (LS)
Mobilization (LS)
Miscellaneous (CS)
Landscaping (LS)
Tota I
$ 1,875,000
2,000,000
1,125,000
500,000
625,000
625,000
500,000
1,500,000
1,519,000
$10,269,000
$ 1,875,000
375,000
2,375,000
1,125,000
2,500,000
750,000
1,000,000
313,000
125,000
625,000
625,000
2,063,000
2,763,000
$16,513,000
*Cost of parking area only, does not include other site plan improvements.
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Alternative C
Removal of curb and pavement (67,000 sq yd)
Earthwork (27,000 cu yd)
Pavement (90,000 sq yd)
Curb (55,000 lin ft)
Retaining walls (53,000 sq ft)
Drainage (LS)
Traffic control (LS)
Bridge (LS)
TRI parking area* (3,000 sq yd)
Stabilize Spout Run embankment (LS)
Mobilization (LS)
Miscellaneous (CS)
Landscaping (LS)
Total
Alternative D
Removal of curb and pavement (67,000 sq yd)
Earthwork (42,000 cu yd)
Pavement (100,000 sq yd)
Curb (55,000 lin ft)
Retaining walls (120,000 sq yd)
Drainage (LS)
Traffic Control (LS)
Bridge (LS)
TRI parking area* (3,000 sq yd)
Stabilize Spout Run embankment (LS)
Mobilization (LS)
Miscellaneous (CS)
Landscaping (LS)
Total
$ 1,875,000
625,000
2,625,000
1,125,000
4,125,000
750,000
1,250,000
625,000
125,000
625,000
750,000
2,500,000
4,669,000
$21,669,000
$ 1,875,000
875,000
3,125,000
1,125,000
9,375,000
875,000
1,750,000
625,000
125,000
625,000
1,000,000
3,625,000
6,813,000
$31,813,000
*Cost of parking area only, does not include other site plan improvements.
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APPENDIX B: METHODOLOGY USED FOR THE
TRAFFIC IMPACT ANALYSIS
Methodology
The procedures used to analyze impacts on the transportation network
were adapted from the ongoing regional transportation planning process
conducted by the Metropolitan Washington Council of Governments. Basic
data were supplied by COG for the years 1980 and 2000; the data were
refined for the analysis of existing (1984) conditions and for the
short-term (1990) and long-term (2000) forecasts of the effects of the
proposed alternatives.
COG is responsible for developing a regional transportation plan under
the requirements of the Federal-Aid Highway Act of 1962 and the Urban
Mass Transportation Act of 1964. By terms of this legislation the process
must be a comprehensive, continuing, and coordinated transportation
planning process, often referred to as the "3-C" transportation planning
process. The National Capital Region Transportation Planning Board sets
the policy for the plan and ultimately adopts the approved plan for the
region.
The long-range element of the "Long Range Transportation Plan for the
National Capital Region" was adopted by the Transportation Planning
Board on May 21 , 1980. A technical assessment of the long-range plan
for the year 2000 was subsequently completed in December of 1982. The
analysis process applied in this study was based on the adopted
long-range plan and the findings in the 1982 systems level reevaluation.
The Analysis Process. A computer modeling technique similar to that
used by COG was used for the GWMP traffic analysis. Several of the
available transportation planning computer programs were evaluated, and
the Urban Transportation Planning System (UTPS), developed and
supported by the U.S. Department of Transportation, was selected. It
has been successfully used by transportation planners and engineers
during the past decade and is generally accepted by the profession for
long-range forecasts and for use in environmental impact statements.
The UTPS typically incorporates a four-step process of determining
trip generation (the number of trips for various purposes that
originate within different parts of a region)
trip distribution (destination of trips)
modal split (the transportation modes--auto, truck, high-occupancy
vehicle, bus, train, bicycle, etc.--used for the trips)
trip assignment (the routes used for the trips)
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Preliminary estimates for the first three factors were provided by COG,
based on projections about the distribution of population and employment.
To gather the data necessary for ongoing land use projections, COG has
divided the Washington metropolitan region into 200 analysis districts
containing 1,345 analysis zones. Working with the cooperating agencies of
the local jurisdictions, COG has developed a range of forecasts about the
future land use patterns of each district and zone. These forecasts are
based on alternative assumptions about low, intermediate, or high levels
of future growth. The most recently adopted forecasts are the "Round
III" forecasts published by COG in 1984. The assumption of intermediate
growth was selected for the assessment of both the short-term and
long-term impacts of the GWMP alternatives. COG used these land use
data to estimate the daily number of trips originating in each district and
zone, and then appropriate modeling techniques were used to determine
the modes and destinations of the trips. COG produced a series of
matrices showing the number of daily vehicle trips made between each
pair of districts, further broken down according to the following trip
types: home-based low-occupancy auto work trips, home-based
high-occupancy vehicle work trips, home-based auto nonwork trips, truck
trips, and miscellaneous trips.
The determination of which routes would be used for these trips required
the development of a composite baseline highway network. The COG year
2000 district-level and zonal-level highway networks were used to develop
the baseline network. All of the assumptions regarding the completion of
the transportation facilities listed above were included except as noted in
the discussion. The number and type of highway facilities incorporated
into the baseline network depended on the location of the analysis unit.
Only the major roadways were included in the outlying analysis units,
while the complete roadway system was analyzed within the EIS study
area. The resulting baseline network contained a total of approximately
5,300 directional highway links. Modifications were then made to the
baseline network to create three alternative networks corresponding to
alternatives B, C, and D.
The year 2000 district-to-district daily trip tables were also modified.
First, the daily trip matrices were adjusted to develop daily trip tables
for the 320 analysis units rather than the 200 districts. The smaller
analysis units were all inside the beltway and consisted mainly of COG
analysis zones and subzones in the Rosslyn area. Trips to and from the
18 districts were allocated to the 138 zones and subzones on the basis of
socioeconomic characteristics.
The modified morning and evening peak-hour trip tables for
miscellaneous, nonwork, and auto work trips were combined and then
assigned to the baseline highway network and the alternative B, C, and
D networks using an all or nothing assignment algorithm.
High-occupancy-vehicle work trips were then assigned using a
capacity-restraint algorithm. The restrictions on certain network links
(for example, no trucks, HOVs during morning or evening peak hour, no
traffic during the morning peak hour) were included in the model. The
resulting computer assignments were manually reviewed, and necessary
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adjustments were then made to develop the traffic projections. Projected
peak-hour volumes for 1990 for 50 critical links were derived by an
interpolation of existing (1984) traffic volumes and the year 2000
projections.
Conversion of Data. The Metropolitan Washington COG data, which are
formatted to provide information for the 24-hour period only, had to be
reformulated to provide data for morning and evening peak-hour travel.
To accomplish this, factors were developed to reflect what percentages of
different kinds of daily trips were made during the morning and evening
peak hours.
The treatment of high-occupancy-vehicle trips also posed a potential
problem. The COG trip tables were developed assuming an HOV-4
requirement instead of the HOV-3 requirement currently enforced on 1-66.
Data provided by the Virginia Department of Highways and Transportation
revealed that vehicular traffic on 1-66 during the peak hour has increased
substantially since January 1984 when HOV-3 went into effect. On the
basis of the best available data, it appears that the vehicular traffic on
1-66 is two to four times higher with HOV-3 relative to the period when
HOV-4 was in effect. For analysis purposes it was assumed that HOV-3
would be in effect on 1-66 in the future, and adjustments were made
accordingly.
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APPENDIX C: CONSULTATION WITH THE
U.S. FISH AND WILDLIFE SERVICE
United States Department of the Interior
FISH AND WILDLIFE SERVICE
DIVISION OF ECOLOGICAL SERVICES
1825B VIRGINIA STREET
ANNAPOLIS. MARYLAND 21401
October 16,-1984
Mr. Gerald D. Patten
National Park Service/Denver Service Center
755 Parfet Street
P.O. Box 25287
Denver, CO 80225
This responds to your September 27, 1984 request for information on the
presence of Federally listed endangered or threatened species within the
area to be affected by the George Washington Memorial Parkway between Spout
Run and Theodore Roosevelt Bridge (Package 836) in Arlington County,
Virginia.
Except for occasional transient individuals, no Federally listed or pro-
posed endangered or threatened species are known to exist in the project
impact area. Therefore, no Biological Assessment or further Section 7
Consultation is required with the Fish and Wildlife Service (FWS). Should
project plans change, or if additional information on the distribution of
listed or proposed species becomes available, this determination may be
reconsidered.
This response relates only to endangered species under our jurisdiction.
It does not address other FWS concerns under the Fish and Wildlife
Coordination Act or other legislation.
Thank you for your interest in endangered species. If you have any
questions or need further assistance, please contact Andy Moser of our
Endangered Species staff at [phone].
Sincerely yours,
G. , A, =.1/Lc5fez-~
~~ZGlenn Kinser
Supervisor
Annapolis Field Office
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GLOSSARY
average daily traffic (ADT)
the total volume of traffic during a given period of time greater than
one day and less than one year, divided by the number of days in
that time period
capacity
the maximum number of vehicles per unit of time that can be
accommodated by a particular roadway segment under the prevailing
roadway and traffic conditions
diverging
a single stream of traffic dividing into two separate streams
level of service
a qualitative measure of traffic flow along a roadway or through an
intersection represented by a rating between A and F, with A
representing little or no delay and F representing extreme congestion
merging
two separate streams of traffic combining to form a single stream
queue
a line of vehicles waiting in a congested lane or on a congested ramp
queue length
the theoretical length of a queue, in this study based on a vehicle
density of 100 vehicles per mile per lane
travel time
the running and delay time required to traverse a specified route
weaving
the crossing of traffic streams moving in the same general direction,
accomplished by merging and diverging
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BIBLIOGRAPHY
ARLINGTON COUNTY DEPARTMENT OF COMMUNITY AFFAIRS
1982a Trends, Hotel Development. Arlington, VA.
1982b "Arlington, Virginia, 1980 Census Tract Data." Arlington,
VA.
1983a Development in the Metro Corridors. Arlington, VA.
1983b Summary of Demographic Changes, 1970-80. Arlington, VA.
1984a "Available Office/Retail Space, Summary." Arlington, VA.
1984b Economic Development Update. Arlington, VA.
1984c Long Range Forecasts: 1985-2010. Arlington, VA.
1984d "Office Development in Arlington County, Virginia, Under
Construction and Site Plan Approved Buildings." Arlington,
VA.
1984e Supplement to Census Highlights #5: Labor Force
Characteristics. Arlington, VA.
BELLOMO-MCGEE, INC.
1984 "George Washington Memorial Parkway, Environmental Impact
Statement, Technical Report on Traffic, Air Quality, Noise."
Prepared for the National Park Service. On file at the NPS
Denver Service Center and George Washington Memorial
Parkway, VA.
1985a "George Washington Memorial Parkway, Traffic Safety and
Improvement Study." Draft. Prepared for the National Park
Service. On file at the NPS Denver Service Center and
George Washington Memorial Parkway, VA.
1985b "Location-Specific Queuing and Delay Analysis of Alternatives
Proposed for the George Washington Memorial Parkway."
Prepared for the National Park Service. On file at the NPS
Denver Service Center and George Washington Memorial
Parkway, VA.
BUILDING OWNERS AND MANAGERS ASSOCIATION (BOMA)
1984 BOMA Experience Exchange Report 1984.
FAIRFAX COUNTY OFFICE OF RESEARCH AND STATISTICS
1984 "Demographic Changes in Planning Districts." Fairfax, VA.
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FEDERAL HIGHWAY ADMINISTRATION, U.S. DEPARTMENT OF
TRANSPORTATION
1984 "George Washington Memorial Parkway Traffic Study at
Theodore Roosevelt Island Parking Area."
GENERAL SERVICES ADMINISTRATION, OFFICE OF PUBLIC BUILDINGS
AND REAL PROPERTY
1983 uarterl Report of Assignment and Utilization of GSA
Controlled Space in the National Capital Region.
GEOLOGICAL SURVEY, U.S. DEPARTMENT OF THE INTERIOR
1964 Geology and Ground-Water Resources of Washington D.C.,
and Vicinity. Geological Survey Water-Supply Paper 1776.
Washington, D.C.: U.S. Government Printing Office.
1984 Engineering Geology and Design of Slopes for Cretaceous
Potomac Deposits in Fairfax County, Virginia, and Vicinity.
Geological Survey Bulletin 1556. Washington, D.C.: U.S.
Government Printing Office.
HUMPHREY, ROBERT L., AND MARY ELIZABETH CHAMBERS
1977 Ancient Washington: American Indian Cultures of the Potomac
Valley. George Washington University Studies, Number Six.
Washington, D.C.
METROPOLITAN WASHINGTON COUNCIL OF GOVERNMENTS
1982 "Final Washington Metropolitan Air Quality Plan for Control of
Ozone and Carbon Monoxide."
1983 "1983 Metro Core Cordon Count of Vehicle and Passenger
Volumes, Summary of Findings." National Capital Region
Transportation Planning Board.
1984a "1984 Beltway Cordon Count of Vehicle and Passenger
Volumes." National Capital Region Transportation Planning
Board.
1984b Cooperative Forecasting, Round III Technical Report, 1984.
Washington, D.C.
MILLER, DAVID V.
1976 The Defenses of Washington During the Civil War. Buffalo,
NY: Copy, Inc.
MONTGOMERY COUNTY PLANNING BOARD
1982a "Economic Characteristics: Commuting, Income, and
Employment." Silver Spring, Maryland.
1982b "Social Characteristics, 1980: Mobility, Families, Poverty,
and Education." Silver Spring, Maryland.
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1984 1983 Report on Comprehensive Planning Policies. Silver
Spring, Maryland.
NATIONAL ACADEMY OF SCIENCES, NATIONAL RESEARCH COUNCIL
1965 Highway Capacity Manual. Highway Research Board Special
Report 87. Washington, D.C.
NATIONAL PARK SERVICE, U.S. DEPARTMENT OF THE INTERIOR
n. d. "Statement for Management, Theodore Roosevelt Island."
George Washington Memorial Parkway, VA.
1963 Geomorphology and Vegetation of Theodore Roosevelt Island,
by Lindsey Kay Thomas, Jr. Scientific Report No. 2.
National Capital Region.
1980 Impact of Three Exotic Plant Species on a Potomac Island, by
Lindsey Kay Thomas, Jr. National Park Service Scientific
Monograph Series, No. 13.
1984a "Statement for Interpretation, South Parkway." George
Washington Memorial Parkway, VA.
1984b "Traffic Operations Study, George Washington Memorial
Parkway." Denver Service Center.
POTTER, STEPHEN R.
1983- "The Indians of Seventeenth Century Fairfax." Fairfax
1984 Chronicles, vol. VIII, no. 4. Fairfax, VA: Fairfax County
Office of Comprehensive Planning.
REED, JOHN C., JR., ROBERT S. SIGAFOOS, AND GEORGE W. FISHER
1984 The Geologic Story of Great Falls and the Potomac River
Gorge. U.S. Geological Survey Bulletin 1471. Washington,
DC: Parks and History Association.
SOIL CONSERVATION SERVICE, U.S. DEPARTMENT OF AGRICULTURE
1976 Soil Survey of District of Columbia. Washington, D.C.:
U.S. Government Printing Office.
TEMPLEMAN, ELEANOR LEE
1959 Arlington Heritage: Vignettes of a Virginia County.
Published by the author.
U.S. DEPARTMENT OF AGRICULTURE, SOIL CONSERVATION SERVICE
1976 Soil Survey of District of Columbia. U.S. Government
Printing Office, Washington, D.C.
U.S. DEPARTMENT OF THE INTERIOR, GEOLOGICAL SURVEY
1964 Geology and Groundwater Resources of Washington, D.C.,
and Vicinity. Geological Survey Water-Supply Paper 1776.
U.S. Government Printing Office, Washington, D.C.
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1984 Engineering Geology and Design of Slopes for Cretaceous
Potomac Deposits in Fairfax County, Virginia, and Vicinity.
Geological Survey Bulletin 1556. U.S. Government Printing
Office, Washington, D.C.
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INDEX
access points, parkway 43
accidents, 2, 48-55, 106, 121, 124-26
ADT, 41-46, 109-11, 114-21
air quality, 31-32, 96-99
alternatives, 7-20
archeological resources, 34, 100
Arlington County Department of
Public Works, 44, 127
Arlington Memorial Bridge, 21
Bellomo-McGee, Inc., 128
capacity, theoretical , 46, 109, 114-21
capacity-deficient locations, 105
Capital Beltway, 39
Capper-Crampton Act, 27, 28
carpool/vanpool, 7, 129
climate, 31
commuter fee, 22
commuter patterns, 41
cost estimates, 135-36
demand, 109, 114-21
District of Columbia Department of
Public Works, 44, 127
design standards, parkway, 23, 61
Federal Highway
Administration, 44, 127
fishing, 23
geologic features, 29
GWMP, boundaries, 28
historic sites, 34
HOV, 21, 39, 129
landscaping, 7, 23, 61-62
lane width, 43
Lee Highway, 22
level of service, 55, 121-23
lighting, 22
Little River shoreline, 23, 103
Lorcom Lane, 8
methodology, 137-39
Metropolitan Washington Council of
Governments, 104, 128, 137-39
Mount Vernon Memorial Highway, 28
Mount Vernon Trail, 37, 102
National Capital Park Commission, 27
National Capital Planning
Commission, 27, 128
noise, 32-34, 100-101
notice of intent, 127
parking lots, 7-8, 37, 43, 102
parkway concept, 27-28
peak-hour traffic volumes, 46-48
Potomac River, 29, 91, 94-95
Potomac River Trail, 38, 94-96, 102
floodplain, 29-30, 92, 94-95, 96
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preferred alternative, 2, 8-9
public comments, 128-32
public transit, 22, 40
reversible lanes, 22
road base, 7
road grade, 42
road surface, 7
Rosslyn Circle, 7, 23
safety improvements, 7, 102, 131
signals, 13, 129
speed limits, 43, 131
study area, 1, 29, 42
Theodore Roosevelt Island, 8, 23,
29, 36-37, 43, 62, 100, 102
threatened or endangered
wildlife, 30, 140
travel times, 109, 114-21
trails, 23, 36-38, 102
traffic impacts, by location
Fort Myer Drive off-ramp, 106
GWMP outbound, 108
Key Bridge off-ramp, 107;
on-ramp, 108
Lorcom Lane/Spout Run
intersection, 106, 108
Lynn Street, 107
Roosevelt Bridge off-ramp, 107-08;
on-ramp, 108
Spout Run/GWMP merge area, 106
trees, 30, 92-93
U.S. Army Corps of Engineers, 96
U.S. Fish and Wildlife Service, 128
140
U.S. Park Police, 8, 44,
94-96
vegetation, 30, 91-96
vegetative succession, 92,
94-95
Virginia Department of Highways and
Transportation, 23, 44, 108, 127, 139
visual quality, 28-29, 61-62, 63-89
(illustrations)
Westchester County Park Commission, 27
wetlands, 91, 94-96
wildlife, 30, 91-92, 94-96
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LIST OF PREPARERS
NPS PLANNING TEAM
Denver Service Center
Keith B. Dunbar, Team Captain/Community Planner
Richard V. Giamberdine, Supervisory Landscape Architect
Maurice L. Miller, Transportation Planner
Linda Romola, Cultural Resource Specialist
Robert Rothweiler, Environmental Specialist
Ann Van Huizen, Outdoor Recreation Planner
Terry Wong, Structural Engineer
George Washington Memorial Parkway
John F. Byrne, Superintendent
Paul Stoehr, Landscape Architect
National Capital Region
Michael Donnelly, Regional Planning Coordinator
CONSULTANTS
Federal Highway Administration, Eastern Direct Federal Division
Gerald J. Lindman, Engineer
Lou Mattia, Engineer
Bellomo-McGee, Inc.
Sal Bellomo, President/Traffic Engineer
Warren Hughes, Associate/Traffic Engineer
National Park Service, Denver Service Center
Jon Haman, Environmental Specialist
COORDINATING AGENCIES
Federal Highway Administration, Eastern Direct Federal Division
Gerald J. Lindman, Engineer
Lou Mattia, Engineer
Arlington County, Department of Public Works
Hank Hume
William Scruggs
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District of Columbia Department of Public Works
George Schoene, Traffic Administrator, Bureau of Traffic
Virginia Department of Highways and Transportation
David R. Gehr, District Engineer
William C. Jeffrey, Assistant State Transportation Planning Engineer
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As the nation's principal conservation agency, the Department of the
Interior has basic responsibilities to protect and conserve our land and
water, energy and minerals, fish and wildlife, parks and recreation
areas, and to ensure the wise use of all these resources. The
department also has major responsibility for American Indian reservation
communities and for people who live in island territories under U.S.
administration.
Publication services were provided by the graphics and editorial staffs of
the Denver Service Center. NPS D-63, August 1985
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