TR9701-CS 970415Sverdrup
Civil, Inc. - Dall~s, Texae Office
4311 Oak Lawn Ave. · Suite 300 · Dallas, TX 75219 · Tele: (214) 520-2116 · Fax: (214) 521-3539
TECHNICAL MEMORANDUM
April 15, 1997
TO:
FROM:
SUBJECT:
Tony Tramel
Dallas County c/o Parsons Brinckerhoff
1701 North Market Street
Suite 410
Dallas, TX 75202
Mark G. Goode, III, P.E.
Proposed Control Area - Northern Section
Job No. 13776
Sverdrup Civil, Inc. has completed an analysis of a section of Belt Line Road and Denton Tap Road
in the cities of Irving and Coppell, Dallas County, Texas. The study boundaries are the intersection
of Denton Tap Road and Parkway Boulevard on the north and the intersection of Belt Line Road and
Oakdale Road on the south. The study area is approximately 14 miles long and includes 34
intersections (see Figure 1). Most of the intersections have existing traffic signals. Two of the
intersections are anticipating traffic signals in the near future to support development that is
underway.
Traffic data have been collected, including hourly directional machine counts, peak hour manual
turning movement counts and travel time runs. Field observations have been made to determine
intersection geometric conditions, lane usage, signal types and presence or absence of pedestrian
signalization.
Proposed Control Area Boundary:
The proposed control area boundary for the northern section is shown in Figure 2. The section
includes the following intersections:
Denton Tap Road / Parkway Boulevard
Denton Tap Road / Sandy Lake Road'
Denton Tap Road / Bethel School Road
Denton Tap Road / Bethel Road
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p~J~RY BLVD.
Figure 1
Sturdy Limits
Sverdrup
Civil, Inc. Dallas, Texas
! ,/
4311 Oak Lawn · Suit~ 300, LB6 · 75219 · Phone: (214) 520-2116 · Fax: (214) 521-3539
Page 2
COPPELL
POP IG, 881
t
'\
Figure 2
"~Eontrol Area Boundary Limits
NORTH
NORTH L~KE P/~RK
----1
I
x~
0 SIGNALIZED
INTERSECTION
...... -gVerdrup
Civil, Inc. Dallas, Tcxas
4311 Oak Lawn · Suite 300, LB6 · 75219 · Phone: (214) 520-2116 · Fnx: (214) 52 ! -3539
Page 3
· Belt Line Road /
· Belt Line Road /
· Belt Line Road /
· Belt Line Road /
· Belt Line Road /
· Belt Line Road /
· Belt Line
· Belt Line
Denton Tap Road / Belt Line Road / Southwestern Boulevard
Belt Line Road / Airline Drive (proposed)
Wrangler Drive
Lakeshore Drive (proposed)
IH 635 Westbound Ramp
IH 635 Eastbound Ramp
Regent Boulevard
Royal Lane
Road / SH 114 Westbound Ramp
Road / SH 114 Eastbound Ramp
This control area was chosen primarily due to the apparent desire for the majority of the traffic to
go from the Coppell area south past the interchange of IH 635 to at least SH 114. In addition, the
existing and proposed traffic signals in this area are generally fairly close together. The only
location where the distance between the signals would indicate the possibility of not coordinating
is between the intersection of Lakeshore Drive and the IH 635 westbound ramp. However, breaking
coordination at this location would be not be consistent with serving the heavy southbound through
movements in the AM Peak Hour that do not mm off Belt Line Road until south of IH 635. An
additional factor that lead to the decision to use the proposed limits for this control area was one of
the outputs provided by the computer program Synchro Professional. This output, called the
"Coordinatability Factor" is an indication of the recommended areas of coordination based on travel
time between the intersections, traffic volumes, platooning of the vehicles, main street volumes and
differences in natural cycle lengths.
Proposed Coordination Across City Limits:
The proposed control area includes traffic signals in both Irving and Coppell. Therefore,
coordination across city limit lines will be necessary. This interjurisdictional coordination can be
most efficiently accomplished by time-based coordination between the signals. Alternatively, it
would also be possible to establish a force account agreement between the cities that would allow
one city to control the other city's signals.
Proposed Cycle Lengths:
Based on the traffic volumes and geometric conditions, we propose to use the following approximate
cycle lengths to get good progression along this section of Denton Tap Road and Belt Line Road:
Time of Day
AM Peak Hour
PM Peak Hour
Off Peak'
Start / End Times
7:00 AM - 9:00 AM
4:30 PM - 6:30 PM
All Other Times
Cycle Length
100 - 120 sec.
100 - 120 sec.
60 - 75 sec.
Direction Favored
Southbound
Northbound
Balanced
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Preliminary Measures of Effectiveness:
The computer programs being used for this analysis are PASSER II and Synchro Professional.
These programs provide a number of measures of effectiveness to evaluate a proposed timing plan
prior to implementing it in the field. In particular, "Progression Band Widths" and "Percentile
Delay" (in seconds per vehicle) will be used to evaluate the projected effectiveness of the proposed
timing plans.
Recommended Hardware Improvements:
During the data collection and preliminary analysis phases of the project, several problem locations
were discovered where the retiming of the traffic signals would be vastly more effective with some
minor modifications to the lane assignments, signal head types and/or the signal operations.
At the intersection of Denton Tap Road and Parkway Boulevard, the eastbound right turn is very
heavy during the times of day when vehicles are approaching or departing the Coppell High School
located just west of the intersection. The eastbound approach at this intersection has a dedicated lei't-
m lane and two through lanes. When a through vehicle chooses the outside lane, the right-turning
traffic queues back a long distance. If this lane were striped for right mm only, the right-ming
traffic would be able to turn on red. An additional improvement that would further improve
operations at this intersection would be the installation of a 5-section "fight-mm overlap signal" that
would be green when the northbound left-mm is being serviced.
At the intersection of Denton Tap Road and Bethel School Road, considerable back-ups occur on
the westbound approach, which has over 300 vehicles mining left between 7:15 and 8:15 AM. This
left-mm movement receives only permitted phasing and must therefore yield to the eastbound traffic.
With some minor improvements to the signal heads, a protected left-mm phase could be
implemented for the westbound traffic only, prior to the permitted phase. This would allow for
more efficient movement of the westbound traffic. A restriping of the eastbound approach to this
intersection also appears to be possible, which would allow the fairly heavy right-tm movement
to have a dedicated lane. Supression of the protected northbound left-turn phase at this location in
the AM Peak would allow for improved southbound progression.
At the intersection of Denton Tap Road and Bethel Road, supresion of the southbound left-turn
phase in the AM Peak would allow for better progression in the northbound direction.
Progression along this stretch or roadway is vastly improved if lead-lag operation can be
implemented at the intersection of Belt Line Road / Denton Tap Road / Southwestern Road. This
can be accomplished without introducing the "Yellow Trap" effect through the use of Dallas display
left-turn heads or non-permissive heads.
~ ~' ~ ~l~'~r~d~ ~~ 4311 Oak Lawn $ Suite 300, LB6 $ 75219 ~' Phone: (214) 520-2116 * Fax: (214) 521-3539
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At the intersection of Belt Line Road and the IH 635 Eastbound Ramp, the eastbound approach to
the intersection is striped for a dedicated left-mm lane and a lane that allows, left tums, throughs and
right tums. Considering the very heavy fight-mm .movement in the AM Peak Hour (over 500
vehicles between 7:15 and 8:15 AM), this approach would be more efficiently served by a dedicated
fight-mm lane and a lane that allows through and left-mm movements. In addition, a right-mm
overlap could be used at this location with the installation of an additional signal head.
Progression along this stretch or roadway is vastly improved if lead-lag operation can be
implemented at the intersection of Belt Line Road and Regent Boulevard. This can be accomplished
without introducing the "Yellow Trap" effect through the use of Dallas display left-mm heads or
non-permissive heads.
If these proposed improvements are performed prior to the implementation of the recommended
timing, the proposed timing will provided much more efficient service to the traveling public.
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