ParkW CC-1/PP-SY 891208I
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THOROUGHFARE ALIGNMENT STUDY
FOR SOUTHWESTERN BOULEVARD
IN COPPELL, TEXAS
Prepared for:
Prentiss Properties Limited, Inc.
and
Santa Fe Pacific Realty
Prepared by:
DeShazo, Starek & Tang, Inc.
330 Union Station
Dallas, Texas
(214) 748-6740
J89310
December 8, 1989
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INTRODUCTION
Southwestern Boulevard is a collector in west Coppe11
between Freeport Parkway and Belt Line/Denton Tap Road.
Prentiss Properties is proposing a Warehouse/Office
commercial development on 328 acres generally bounded by
Southwestern Blvd. to the north, Belt Line Road to the east,
Cowboy Drive to the south and Freeport Parkway to the west.
Santa Fe Pacific Realty is proposing a similar development
on 225 acres located between Royal Lane, the St. Louis &
Southwestern Railroad tracks, LBJ Freeway and both sides of
Freeway Parkway. These two developments, by virtue of their
size and location, have a significant impact on the area
thoroughfares. Conversely, the alignment and sizes of these
thoroughfares have a significant impact on the site plans of
these developments. The location of the Prentiss Properties
and Santa Fe Pacific developments are shown in Figure 1.
PURPOSE
The purpose of this study is to analyze various alignments
of Southwestern and Gateway Blvd. utilizing predicted year
2010 traffic with the two developments in place. This will
be accomplished in the following steps:
o Obtain current City of Coppell Thoroughfare Plan.
o Obtain current year 2010 traffic projections.
o Determine year 2010 base volumes utilizing existing
counts, thoroughfare plan and year 2010 traffic
projections.
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Add development traffic to year 2010 base link
volumes.
Determine best alignment based on year 2010 link
volumes, impact on site plan, and impact on adjacent
intersections.
In a companion study, roadway sizing will be based on year
2010 link volumes. In a study to follow, horizontal
alignments of roadways built by the developers will be
determined through standards set by the Department of Public
Works.
ALTERNATIVE ALIGNMENTS
Four alternative alignments for Southwestern and Gateway
Blvd. are'being studied. Alternative 1 is the City of
Coppell's Thoroughfare Plan alignment, see Figure 2. The
alignment first proposed by Prentiss Properties is shown in
Figure 3. Alternative 3 is a variation of the original
Prentiss alignment. The difference being that as
Southwestern approaches Freeport Pkwy. from Belt Line, it
continues its westerly direction parallel to the RR tracks
rather than veering to the southwest, see Figure 4.
Alternative 4 is similar to the Thoroughfare Plan between
Royal Ln. and Freeport Pkwy., however, east of Freeport the
larger roadway ties into the minor roadway adjacent to the
RR tracks, see Figure 5.
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PROJECTIONS
Year 2010 peak hour traffic volume projections for the study
area were developed through a four-step traffic modeling
procedure:
Estimate year 2010 24-hour background or "base"
volumes, for the study area that assume no develop-
ments on the Prentiss or Santa Fe properties.
Calculate year 2010 peak hour "base" volumes that
represent ten percent of the 24-hour volumes.
Calculate year 2010 peak hour volumes that represent
traffic generated by the Prentiss and Santa Fe
properties.
Add the "base" volumes from step %2 to the site-
generated volumes in step %3 to create total year
2010 peak hour traffic volume estimates· This
assumes full buildout of the properties in the year
2010 per the submitted site plans·
Details of this procedure are described below.
Year 2010 24-Hour Base VOlumes
Information assembled for this stage of the subarea traffic
modeling procedure consisted of:
Available daily traffic counts. DeShazo, Starek &
Tang performmed 24 hour machine counts on Royal Ln and
Freeport Pkwy. south of Bethel Rd., and on Bethel Rd.
east and west of Freeport Pkwy. Manual turning
movement counts were performed at the intersection of
Belt Line and Denton Tap Rd. from 7-9 AM and 4-6 PM to
determine morning and evening peak hour turning
movement volumes.
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Population and employment estimates, by traffic survey
for 1986 and 2010 prepared by the North Central Texas
Council of Governments (NCTCOG).
Year 2010 daily traffic volume estimates obtained from
the "20-20-27" traffic model developed by the State
Department of Highways and Public Transportation
(SDHPT).
Year 2010 dily traffic volume estimates obtained from
NCTCOG's MTAP (Multi-modal Transportation Analysis
Process) traffic model.
o Thoroughfare plans for the City of
Estimated current 24 hour traffic volumes are shown in
Figure 6, the Belt Line/Denton Tap peak hour turning
movement counts are shown in Figure 7 . NCTCOG's population
and employment estimates for the year 2010 were used in both
the SDHPT and NCTCOG traffic models. Estimates for the City
of Coppell as submitted by NCTCOG were as follows:
1986 2010
Population 10,800 31,700
E~ployment 2,100 6,800
An examination of the year 2010 traffic volume plots
revealed that Prentiss and Santa Fe developments were not
included in the employment forecasts. It was therefore
appropriate to treat these computer estimates as "base" year
2010 volumes that do not represent the traffic generated by
the Prentiss or Santa Fe properties. This was,done in order
to generate a worst-case forecast scenario.
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BELT LINE
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FIGURE 7
AM and PM Peak Hour Turning Movement Counts
at Belt Une/Denton Tap Intersection
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BUILDING USE
TABLE I
PRENTISS PROPERTIES SITE
TRIP GENERATION
AMOUNT
PM PK HR TRAFFIC
IN OUT TOTAL
i WAREHOUSE
2 WAREHOUSE
3 WAREHOUSE
4 WAREHOUSE
5 WAREHOUSE
6 WAREHOUSE
7 WAREHOUSE
8 WAREHOUSE
9 WAREHOUSE
10 WAREHOUSE
11 WAREHOUSE
12 WAREHOUSE
13 WAREHOUSE
14 WAREHOUSE
15 WAREHOUSE
16 WAREHOUSE
17 WAREHOUSE
18 WAREHOUSE
19 WAREHOUSE
20 WAREHOUSE
21 WAREHOUSE
22 WAREHOUSE
23 WAREHOUSE
24 WAREHOUSE
25 WAREHOUSE
26 WAREHOUSE
27 WAREHOUSE
28 WAREHOUSE
29 WAREHOUSE
30 WAREHOUSE
31 WAREHOUSE
32 WAREHOUSE
33 WAREHOUSE
TOTAL'
O1 OFFICE
02 OFFICE
03 OFFICE
04 OFFICE
05 OFFICE
06 OFFICE
07 OFFICE
TOTAL=
140,800 52 89 141
179,200 67 114 181
80,000 29 49 78
82,000 30 50 80
175,000 65 111 177
175,000 65 111 177
132,000 49 83 132
132,000 49 83 132
133,000 49 84 133
133,000 49 84 133
132,000 49 83 132
132,000 49 83 132
156,000 58 99 157
150,000 56 95 150
135,360 50 85 135
136,000 50 86 136
194,000 73 124 197
150,000 56 95 150
160,000 60 101 161
134,000 49 84 134
135,000 50 85 135
130,000 48 82 129
194,000 73 124 197
140,000 52 88 140
122,000 45 76 121
156,000 58 99 157
145,000 54 91 145
170,000 63 108 172
105,000 38 65 103
105,000 38 65 103
78,000 28 48 76
100,000 36 62 98
112,500 41 70 111
4,533,860 1,677 2,855 4,532
231,000 63 331 394
258,000 69 363 432
107,500 33 176 209
82,000 27 140 167
143,500 42 223 266
151,700 45 234 278
168,000 48 254 303
1,141,700 328 1,721 2,049
SITE TOTAL-~ 5,675,560
2,005 4,577 6,581
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TABLE II
SANTA FE PACIFIC SITE
TRIP GENERATION
PARCEL USE AMOUNT
SF1 OFFICE 379,894
109.2 AC WAREHOUSE 1,508,616
PM PK HR TRAFFIC
IN OUT TOTAL
667 1523 2,190
SF2 OFFICE 90,451 159 363 522
26.0 AC WAREHOUSE 359,194
SF3 OFFICE 123,500 217 495 712
35.5 AC WAREHOUSE 490,438
SF4 OFFICE 116,542 205 467 672
33.5 AC WAREHOUSE 462,808
OFFICE 710,387
WAREHOUSE 2,821,056
3,531,443 1,248 2,848
SITE TOTAL-
4,096
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Manual adjustments were made to the computer estimates to
reflect traffic model errors related to large analysis zones
and inadequate approach links.
The resulting year 2010 24 hour base volumes for each
alternative alignment are shown in Figures 8 through 11,
respectively. The critical design hour for commercial
development is typically the p.m. peak hour. 24 hours
volumes are multiplied by 10% to estimate "peak hour#
volumes. The estimated year 2010 p.m. peak hour base
traffic volumes for each alternative alignment are shown in
Figures 12 through 15, respectively.
TRIP GENERATION
The site generated traffic for the proposed developments is
shown in Table I and II. The trip generation rates used are
from the Institute of Transportation Engineers Trip
Generation Manual. The proposed Prentiss Properties
development conceptual plan shows thirty three warehouse
buildings averaging 140,000 s.f. each, for a total of
4,533,860 s.f of warehouse. Seven office buildings were
shown, averaging 163,000 s.f., for a total of 1,141,700 s.f
office. The total site square footage is estimated to be
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5,675,560 s.f.. The Santa Fe Pacific development plan does
not specify buildings and usage, but a similar density of
warehouse and office base been suggested, therefore the
traffic generated on the Prentiss Properties site is
factored down by area on each of the Santa Fe Pacific
parcels. To account forthe impact of site generated truck
traffic, the warehouse volumes are increased 20%. One truck
is assumed to be equivalent to two passenger cars and
warehouse traffic is assumed to be 20% trucks. This
increase in average projected daily traffic coupled with the
total assumed buildout of the site plans by the year 2010
represent a worst case scenario.
TRIP DISTRIBUTION
After performing trip generation, the trips resulting from
the proposed developments are distributed to the area street
system. Figure 16 shows the orientations used for
distribution. Figures 17 through 20 show the development
traffic on each alternative alignment, respectively.
Figures 21 through 24 show the sum of the 2010 pm base plus
site traffic on each alignment, respectively.
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ALIGNMENT CHARACTERISTICS
Alternative 1:
o Provides for through movement from Belt Line Rd. to
Royal Ln.
o Additional collector roadway provides interior
circulation.
o Horizontal alignment of Gateway is straighter and would
allow higher design speeds.
o Gateway Blvd. in conjunction with Grapevine Creek
greatly impairs the ability to develop warehouse-type
uses due to its close proximity to the RR tracks, and
the need to provide RR access would require numerous
crossings.
o This alternative is costly because of two major
crossings of Grapevine Creek.
o Bethel and Gateway form one east/west corridor, and
gateway and I.H. 635 form another east/west corridor.
In the Bethel/Gateway corridor the STL & SW RR tracks
form a major barrier.
o As presently layed out heavy interior site truck
traffic will load on Gateway intermixing with through
traffic thereby impeding the through movement.
o The close proximity of the Gateway/Southwestern
intersection to the Gateway/Belt Line intersection
reduces the capacity of Gateway Blvd.
Alternative 2:
o Provides direct through movement from Royal Ln. to Belt
Line.
o More economical in that it only has one crossing with
Grapevine Creek.
o The alignment of Southwestern provides a buffer between
the existing land uses to the north and the proposed
future land uses to the south.
o The location of Grapevine Creek to the southeast and
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the RR tracks to the north limit the amount of
development in this area thereby increasing the through
movement capacity.
o The alignment of Southwestern will require only one
rail spur crossing between Freeport and Belt Line, and
potentially no crossings west of Freeport.
o This alignment provides for better utilization of land
in developing efficient site development plans.
Alternative 3:
o Provides the most direct route from Belt Line to Royal.
o More economical in that it only has one crossing with
Grapevine Creek.
o The alignment of Southwestern provides a buffer between
the existing land uses to the north and the proposed
future land uses to the south.
o Greatly impacts the Santa Fe tract in that it makes the
development of warehouse uses extremely difficult.
o The need to provide RR access would require
numerous crossings to serve warehouse uses south of the
road.
Alternative 4:
o Provides least capacity of all alternatives and reduces
the ability to carry through movements from Royal to
Belt Line.
o This type of thoroughfare plan is inefficient in terms
of land development.
o In Santa Fe tract numerous rail spur crossings along
the northernmost collector would occur.
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CONCLUSION
Due to the detriment to the Santa Fe tract, Alternatives 3
and 4 are less acceptable alternatives. They impact the
ability to develop the land efficiently and encourage
numerous spur rail crossings and in the case of Alternative
4, provides less roadway capacity capabilities. Summarizing
the differences between Alternative 1 and 2, Alternative 2
provides a more acceptable alignment to Alternative 1 due to
the following reasons=
o Provides an alignment that is more conducive to a site
development plan.
o Provides more capacity to through movements by limiting
the amount of local traffic, particularly truck traffic
that would use this street for interior circulation.
o Less costly, only requires one creek crossing.
o Alternative 2 in conjunction with the RR tracks
provides a buffer between the land uses to the north
and the proposed land uses to the south.
o Has less impact on the Denton Tap/Belt Line
intersection due to better distribution of interior
site generated traffic between Freeport and Belt Line.
In conclusion Alternative 2 is the more efficient alignment
for Southwestern Blvd. between Royal Ln. and Belt Line Rd.
and is the route supported by Prentiss Properties and Santa
Fe Pacific Realty.