LETTER TO H.M. SHAVER FROM JOHN P. FOWLER, II

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP89-00244R001403260037-1
• Release Decision: RIFPUB
• Original Classification: K
• Document Page Count: 5
• Document Creation Date: December 27, 2016
• Document Release Date: November 30, 2011
• Sequence Number: 37
• Publication Date: February 18, 1986
• Content Type: LETTER

Declassified and Approved For Release 2011/11/30: CIA-RDP89-00244R001403260037-1
Devaterry & Davis
Engineers 8401 Arlington Boulevard
Architects Fairfax, VA 22031
Planners 703 849-0100
Surveyors
February 18, 1986
Mr. H.M. Shaver, Jr.
State Location & Design Engineer
Commonwealth of Virginia
Department of Highways El Transportation
1221 East Broad Street
Richmond, Virginia 23219
Re: CIA Entrance at Route 123 - Phase II
Comparative Evaluation of Signalized Intersections
Route 193 Intersection with Route 123
Dear Mr. Shaver:
Furnished, as an attachment to this letter, is a detailed comparison of the traffic signal
system associated with two alternative designs for the referenced Project. The first
alternative evaluated is our proposed design as submitted to the Department previously
and which corresponds to the Alternative 2 Plan adopted for project implementation.
The other design evaluated, designated Alternative B, involves an offset between Route
193 and the Potomac School Road intersections along the axis of Route 123. The latter
scheme evolved out of discussions at the CIA Advisory Task Force Meeting held on
January 29, 1986.
Also furnished during our meeting of February 19th are prints of drawings showing the
Proposed Design and Alternatives A and B as well as prints of cross sections showing
berm widths and heights which would result from implementation of either of the three
alternatives.
Prints of alternative berm treatments are also furnished. These depict increases in
height of berm or screening which could result from changes in cross section, slope
rate, or from installation of a precast concrete panel screen wall. Lastly, we are
furnishing a qualitative evaluation of the three plans in which we list advantages and
disadvantages of each.
In summary, the proposed design provides a significantly better level of service for
traffic operations along Route 123 when compared with the offset intersection design
(Alternative B). Incremental increases in delay range between 22% and 78k and levels
of service drop from D to E with the offset intersection. Another very significant
disadvantage of the offset design is that it is not readily widened from two to three
lanes in each direction should that eventuality arise.
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Declassified and Approved For Release 2011/11/30: CIA-RDP89-00244R001403260037-1 41e. VA
Declassified and Approved For Release 2011/11/30: CIA-RDP89-00244R001403260037-1
Mr. H.M. Shaver, Jr.
Page -2- February 18, 1986
I trust that the enclosed material satisfactorily provides the information which you
requested.
Yours very truly,
DEWBERRY & DAVIS
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John P. Fowler: II, P.E.
Managing Prtncipal
I
'JPF:rad
Dewberry & Davis
Declassified and Approved For Release 2011/11/30: CIA-RDP89-00244R001403260037-1
Declassified and Approved For Release 2011/11/30: CIA-RDP89-00244R001403260037-1
CIA ENTRANCE AT ROUTE 123 - PHASE II
QUALITATIVE COMPARISON OF ALTERNATIVES
Description of Alternatives
Proposed Design
Route 193 aligned opposite Potomac School Road at intersection with Route 123. About
200' of tangent approach on Route 193.
Alternative A
Route 193 aligned opposite Potomac School Road at intersection with Route 123. Route
193 approach to intersection on curve.
Alternative B
Route 193 intersection with route 123 offset about 80' east of potomac School Road
intersection. Route 193 approach to intersection on tangent with a 90? angle of intersection.
Proposed Design
Alternative A
Advantages
Best combination of
alignment and signal
installation
Can be readily widened
Provides minimum
acceptable level of
service
Provides slightly
greater separation from
Evermay - Section
VII
Alternative B Best approach alignment
for Route 193
Greater separation
to Evermay - Section
VII
Disadvantages
Closest to Evermay
Section VII
Unsatisfactory approach
alignment on Route 193
Unsafe for tandem left design
Slight impact on signal
efficiency - difficult to
quantify
Unacceptable levels of
service for signal installation
- as measured by delays
Widening to three lanes each
way difficult to accomplish
Intersection channelization
and signing is complicated
and difficult to do effectively
Dewberry & Davis
Declassified and Approved For Release 2011/11/30: CIA-RDP89-00244R001403260037-1
Declassified and Approved For Release 2011/11/30: CIA-RDP89-00244R001403260037-1
CCMPARISCN OF SIGNAL INSTALLATION
PROPOSED DESIGN AND AL'TERNATIVE B
RATING OP OVERALL INTERSECTION
AM PM
PEAK HOUR PEAK HOUR
PROPOSED DIMIGN
Average Delay 37.6 sec./veh. 29.6 sec./veh.
Level of Service
No. of Vehicles 4,414 5,821
ALTERNATIVE B
Averaoe Delay 46.0 sec./veh. 52.8 sec./veh.
Level of Service
Nc. of Vehicles 4,414 5,821
Increase in Delay
PENK HOUR
DIRECTICN FLOW
PROPOSED DSIGN
+22% +78%
ROUTE 123
EASI'BCOND WIISTBOUND
123 123
Average Delay 25.0 sec./veh.
Level of Service
No. of Vehicles 2,232
ALTERNATIVE B
29.7 sec./veh.
3,953
Average Delay 31.0 sec./veh. 50.8 sec./veh.
Level of Service
No. of Vehicles 2,232 3,953
Increase in Delay
+24% +71%
Declassified and Approved For Release 2011/11/30: CIA-RDP89-00244R001403260037-1
Declassified and Approved For Release 2011/11/30: CIA-RDP89-00244R001403260037-1
AVERAGE DEEM
No. of Vehicles
Average Delay:
Proposed Design
Alternative B
Percent Greater
As
ROUTE 193 POTOMC SCHOOL RD.
1,503 443
74.8 sec./veh. 65.5 sec./veh.
102.2 sec./veh. 92.6 sec./veh.
37% 41%
Alternative B Level of Service
Delays on Alternative B
PROPOSED DESIGN: 3 seconds for all yellow phases, aggregate 12 seconds lost
time.
ALTERNATIVE A:
ALTERNATIVES:
4 seconds for southbound turn yellow, aggregate 13 seconds.
5 seconds to east and west and north and south through
yellow, aggregate 18 seconds.
Therefore, delays on A about 1/6 of difference between Proposed Desian &
Alternative B greater than Proposed Design.
(i.e., cycle time increases).
Declassified and Approved For Release 2011/11/30: CIA-RDP89-00244R001403260037-1