Freeport SY-140609
Prologis Coppell Freeport Parkway
Traffic Evaluation
Technical Memorandum
TO: Mr. James McGill
FROM: Scott Booth, PE, PTOE
DATE: June 9, 2014
RETraffic Evaluation of Prologis Development in Coppell, Texas
:
Halff Associates, Inc. (Halff) has been retained by Prologis to conduct a traffic evaluation for the
proposed warehouse development in Coppell, Texas. The evaluation consisted of estimating the
volume of traffic on the proposed section of Freeport Parkway between SH 121 and Sandy Lake
Road (See Figure 1 below). This traffic estimation included both background pass-through traffic
and traffic related to the proposed development. The evaluation also included a review of the
traffic demand at the development driveways and the required storage for left-turn and right-turn
lanes if needed. A copy of the site plan is attached.
Figure 1 Location of Proposed Section of Freeport Parkway
METHODOLOGY
To develop background traffic volumes, 24-hour count data was collected at sections of Freeport
Parkway north and south of the proposed new section. Using that data, the estimated
background traffic volume was calculated. Traffic related to the development was calculated by
generating trips for the development and distributing them on the roadway system. These trips
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Prologis Coppell Freeport Parkway
Traffic Evaluation
were combined with the projected background traffic volumes to arrive at a total projected traffic
volume on the proposed section of Freeport Parkway.
With the trips related to the development distributed on the roadway system and at the
development driveways, Halff examined the need for right-turn and/or left-turn lanes serving the
driveways. For median openings with left-turns already proposed, Halff determined minimum
storage lengths based on the projected development traffic volumes.
BACKGROUND TRAFFIC VOLUMES
Traffic volumes over a weekday 24-hour period were collected at several locations. Table 1
below summarizes the traffic count data. Copies of the full data are also attached to this
memorandum.
Table 1 24-hour Traffic Volumes
In looking at Figure 1 above, the proposed section of Freeport will provide a more direct
connection to SH 121 for both traffic traveling on Sandy Lake Road and areas south of Sandy
Lake Road. It also ties into the SH 121 frontage roads near entrance and exit ramps to and from
the north. Therefore, traffic that is traveling west on Sandy Lake Rd to northbound SH 121 will
likely use the new section of Freeport Parkway. This also applies to traffic traveling on
northbound Freeport Parkway. The reverse routing would be similarly desirable.
Based on the traffic data, it is estimated that 40 percent of the traffic on Freeport Parkway would
use the new section to reach SH-121. It is also estimated that approximately 30 percent of the
traffic on Sandy Lake Road (historically around 10,000 vehicles per day) would use the new
section of Freeport Parkway. Combining these two traffic streams results in approximately
5,500 vehicles per day on the new section of Freeport Parkway between SH 121 and Sandy Lake
Road when it is first opened. Given the continued growth in the area, it is anticipated that
background traffic will continue to increase over time, especially when the two-lane section of
Freeport Parkway just south of Sandy Lake Road is widened.
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Prologis Coppell Freeport Parkway
Traffic Evaluation
DEVELOPMENT TRAFFIC VOLUMES
Trips for the proposed development were generated based on the ITE Trip Generation Manual -
Ninth Edition. Table 2 below contains a summary of the trip generation for all parts of the
development at build-out.
Table 2 Trip Generation Summary
24-hour
AM-peak PM-peak
Weekday
Land Use Independent
Units
(ITE Code) Variable
In Out Total In Out Total Total
High-Cube
Warehouse per 1000 gsf 843.4
64 29 93 31 70 101 1,417
(152)
Warehouse
per 1000 gsf 760.3
180 48 228 61 182 243 2,707
(150)
Total Trips
244 77 321 92 252 344 4,124
In looking at Table 2 above, the proposed development will add approximately 4,100 trips per
day on the new section of Freeport Parkway, which accounts for approximately 43 percent of the
overall volumes at opening day. As background volumes continue to grow, the development will
represent a smaller portion of the overall traffic volumes.
The distribution of trips related to the development is anticipated to significantly favor the SH
121 corridor. It is estimated that 80 percent of the development traffic will be to and from the
north with 35 percent coming from the northeast on SH 121, another 35 percent from the
southwest on SH 121 and 10 percent to and from Freeport Parkway north/west of SH 121. The
remaining 20 percent would be from the south, with 10 percent coming from the west and five
percent from the east on Sandy Lake Road and the remaining five percent from the south on the
existing section of Freeport Parkway.
TURN LANE EVALUATIONS
Deceleration lanes are used to separate traffic that is slowing to turn right (or left) from the
through traffic traveling along a roadway. The need for deceleration lanes is based on several
factors, such as, volume of turning traffic, volume of through traffic, volume of opposing traffic
(i.e. traffic that prevents a permissive left turn), and the vehicle mix (i.e. trucks versus cars).
Right-Turn Deceleration Lanes
For right-turn deceleration lanes, it is generally recommended that a deceleration lane be
considered if the number of right-turning vehicles on facilities with a posted speed limit less than
or equal to 45 miles per hour exceeds 60 vehicles in any one hour period (TxDOT standard).
With the majority of the traffic arriving from the north and given that four of the five warehouse
buildings are on the east side of Freeport Parkway served by five driveways, no one driveway is
projected to exceed the 60 vehicles threshold in a one hour period. With three driveways serving
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Prologis Coppell Freeport Parkway
Traffic Evaluation
Building 5 on the west side of Freeport Parkway, no one drive is projected to exceed the 60
vehicles threshold in a one hour period.
It is recommended that a right-turn deceleration lane be considered on Freeport Parkway at the
westbound approach to the northbound SH 121 frontage road. A review of the proposed
schematic shows this already being included. Storage length should be maximized by starting a
short taper section (50 feet) just north of the northernmost development driveway and extending
the full lane to SH 121.
It is also recommended that a westbound right-turn deceleration lane on Sandy Lake Road at
Freeport Parkway be considered. The need for the right deceleration lane at this location is not
due to the development traffic (only 12 vehicles related to the development in highest hour), but
due to the background traffic that will use the new section of Freeport Parkway to access
northbound SH 121.
Left-Turn Deceleration Lanes
Left-turn deceleration lanes are already being proposed at the major development driveways,
therefore, no additional recommendations are necessary. The highest volume anticipated at any
of the left-turn lanes is 78 vehicles per hour, which is at the main driveway serving Buildings 3
and 4 during the AM peak hour. Given an anticipated opposing through volume of 350 vehicles
per hour, the southbound left-turn should not experience any significant queuing during the peak
hours. Recommended storage length for the southbound left-turn lane would be a minimum of
250 feet with an additional taper section per City of Coppell standards. This same
recommendation (250 feet of storage plus taper) applies to the main driveway serving Buildings
2 and 3. For the median opening serving Building 1 and the opening at the northern most
driveway, the southbound left-turn volumes are significantly lower and a minimum of 150 feet of
storage is recommended.
Although development volumes at the intersection with Sandy Lake Road will be minimal, it is
anticipated that there will be significant background traffic volumes for the southbound left-turn.
Therefore, it is recommended that a minimum of 250 feet of storage be provided at the
southbound approach to Sandy Lake Road.
At the intersection with the SH 121 frontage roads, the proposed design is calling for a full lane
of left-turn storage between the frontage roads. It is also recommended that near side storage
for left-turning vehicles be provided as well and that the length be maximized dependent on
conditions with the median opening serving the northern most driveways.
WESTBOUND QUEUE AT SH 121
Concern has been expressed regarding the possible westbound queue on Freeport Parkway at
northbound SH 121 extending back to the east and blocking the median opening (approximately
400 feet from the northbound frontage road) that serves the warehouse development as the
adjacent two parcels. Therefore, it was necessary to generate traffic volume projections for the
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Prologis Coppell Freeport Parkway
Traffic Evaluation
PM peak hour for the intersections of Freeport Parkway at both northbound and southbound SH
121.
The volumes were generated based on a combination of development traffic combined with
projected background traffic derived from the count data as discussed above. These volumes
were then input into a traffic analysis software package (Synchro 8) to analyze the operation of
the intersections. Geometry of the intersections for the future condition was based on schematic
drawings from TxDOT.
Based on projected volumes at build-out of the development, the westbound queue is expected to
th
average approximately 70 feet in length. The maximum queue (95 percentile queue) is
anticipated to be less than 160 feet. Copies of the Synchro reports are attached.
It is Halffs opinion that the anticipated queue on the westbound approach of Freeport Parkway
at SH 121 will not significantly impact the operation of the median opening serving the
development and that based on the projected volumes, the provided queuing/stacking space is
adequate. For the queue to extend more than 400 feet and block the median opening, westbound
traffic volumes would need to be three times the projected volumes.
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TEXAS3200 AND 3202 STATE HIGHWAY 121, COPPELL,
PROLOGIS PARK ONE TWENTY ONE
EXISTING CURB LINE
EXISTING CURB LINE
(MAINTAINED BY PROLOGIS)
PROLOGIS
DRAINAGE CHANNEL
40' WIDE DRAINAGE CHANNEL
MAINTAINED BY
(26) FUTURE PKG. SP.
118'-0"
@ 152.15'@ 149.37'@ 225.85'
12'-0"62'-0"
12'-0"
540'-0"37'-0"84'-0"395'-0"40'-0"62'-0"190'-0"140'-0"130'-0"230'-0"
10'-0" MIN.185'-0"185'-0"130'-0"180'-0"
31'-0"
10'-0"
10'-0"10'-0"
PKG. SP.
(11) FUTURE
PARKWAY
FREEPORT
FREEPORT PARKWAY (VARIABLE WIDTH R.O.W.)
PROPOSED
30' R.O.W.
NORTHWESTERN DRIVE
62'-0"
118'-0"
123'-0"62'-0"
81'-0"104'-0"
62'-0"
123'-0"
G:\PROLOGIS\12798-Callejo Land\PD Submittal\798-PD Concept Plan 050214.dwg, 5/2/2014 11:56:19 AM, 1:1
HCM Signalized Intersection Capacity Analysis
HCM Signalized Intersection Capacity Analysis
Queues
Queues