Item 5 - Queuing and Signal Warrant Study1201 North Bowser Road
Richardson, Texas 75081-2275
Technical Memorandum
TO: Chris Lott
FROM: Scott Booth, PE, PTOE
DATE: October 23, 2018
RE : Queuing and Signal Warrant Study – Southlake Mixed-Use Office Addition
Introduction
Halff Associates, Inc. (Halff) was retained by North Carroll 114 Properties, LLC (Client) to
prepare a Queuing and Signal Warrant Study supporting the proposed expansion of the mixed-use
office located in the northwest quadrant of Carroll Avenue and Lakewood Drive in Southlake,
Texas. An aerial image of the location and study intersection is shown in Figure 1 below.
Figure 1 - Aerial View of Site and Study Intersection
The proposed expansion increases the single-story office building size by 5,150 square feet, to a
total of 11,750 square feet leasable area. There is a 450 square foot entry that brings the total
building size to 12,200 square feet. With the proposed expansion, the existing driveway (currently
located on Carroll Avenue just north of Lakewood Drive) is proposed to be relocated to Lakewood
Drive. A copy of the proposed site plan with the proposed driveway relocation is attached.
10/23 /2018
North Carroll 114 Properties, LLC
Queuing and Signal Warrant Study
- 2 -
The City of Southlake has requested that a queuing study for the eastbound approach of the
Lakewood Drive and Carroll Avenue intersection be performed to determine the potential impact
of the proposed change in access. In addition, the City requested that a Signal Warrant Study at
the intersection be conducted to determine if future signalization is warranted.
Data Collection
Turning movement counts were collected at the study intersection and driveway during the
weekday AM peak (7:00 to 9:00) and PM peak (4:00 to 6:00) hours. Based on the data collected,
it was determined that 7:15 to 8:15 is the morning peak hour and 4:15 to 5:15 is the afternoon peak
hour. In addition to the peak hour data, 24-hour approach counts were collected at the intersection
of Lakewood Drive and Carroll Avenue. Copies of the traffic data are attached.
Trip Generation and Distribution
Using the collected traffic data, the peak hour trip generation for the existing office for the morning
and the afternoon were determined. Based on that data, the office currently generates nine (9) trips
(8 in, 1 out) in the AM peak and 24 trips (7 in, 17 out) in the PM peak. Using the proposed increase
in the size of the office, a 78 percent increase, a straight-line projection for expected trips was
calculated. With the proposed 11,750 square foot office the projected trips for the site would
consist of 16 trips (14 in, 2 out) in AM peak and 42 trips (12 in, 30 out) in the PM peak.
Figure 2 below shows the existing turning movement volumes at the study intersection and
driveway.
Figure 2 – Existing Volumes
AM Peak 100
PM Peak (100)
North Carroll 114 Properties, LLC
Queuing and Signal Warrant Study
- 3 -
Trips related to the site were then redistributed based on the proposed relocation of the site
driveway to Lakewood Drive. Figure 3 below shows the existing turning movement volumes at
the study intersection, but with the site driveway relocated to Lakewood Drive and the trips related
to the site adjusted to reflect the change.
Figure 3 – Volumes with Relocated Site Driveway
The next figure, Figure 4, shows the proposed driveway configuration, but includes the increase
in site related trips due to the new office space. This figure represents the projected volumes at
the intersection of Carroll Avenue and Lakewood Drive with the proposed office addition being
constructed.
Figure 4 – Volumes with Relocated Site Driveway
AM Peak 100
PM Peak (100)
AM Peak 100
PM Peak (100)
North Carroll 114 Properties, LLC
Queuing and Signal Warrant Study
- 4 -
Queuing Study
Using the turning movement volumes from Figure 2 and Figure 4, queues for the left turn
movement on the eastbound approach of Lakewood Drive were compared for the existing
condition and the future condition (with relocated driveway and additional office space). Table 1
below summarizes the eastbound queues for the given scenarios.
Table 1 – Queuing Analysis Summary
Scenario
95 th Percentile Queue (Max Queue)
Vehicles Length (ft)
AM Peak - Existing < 1.0 < 20
PM Peak - Existing < 1.0 < 20
AM Peak - Proposed < 1.0 < 20
PM Peak - Proposed 1.3 32
In the table above, the queue shown is the 95 th percentile queue or max queue. Stated another way;
95 percent of the time, the queue at the eastbound approach will not be any longer than that listed
in the table and most likely will be shorter. The queues for the right-turn movement from
Lakewood Drive are negligible in length during both the AM and PM peak hour, even with the
addition of traffic related to the site.
Signal Warrant Study
A signal warrant study consists of the examination of nine warrants, which are:
• Warrant 1: Eight-Hour Vehicular Volume
• Warrant 2: Four-Hour Vehicular Volume
• Warrant 3: Peak Hour
• Warrant 4: Pedestrian Volume
• Warrant 5: School Crossing
• Warrant 6: Coordinated Signal System
• Warrant 7: Crash Experience
• Warrant 8: Roadway Network
• Warrant 9: Intersection Near a Grade Crossing
According to the Texas Manual of Uniform Traffic Control Devices (TxMUTCD), a traffic control
signal should not be installed unless one of the above warrants is met, but meeting a traffic signal
warrant does not automatically justify the need for a traffic signal. For warrants based on traffic
volume thresholds, the threshold may be reduced under certain conditions such as an isolated
signal with a population less than 10,000 individuals, or if the posted (or 85 th percentile) speed on
the major road is greater than 40 miles per hour. Since the posted speed limit on Carroll Avenue
does not exceed 40 miles per hour, the reduced thresholds are not applicable to the study
intersection.
North Carroll 114 Properties, LLC
Queuing and Signal Warrant Study
- 5 -
Based on a review of the above warrants and the given conditions at the study intersection, it was
determined that Warrants 4, 5, 6, 7 and 9 were not applicable. This leaves warrants 1, 2, 3, and 8,
which are based on vehicle volumes at the study intersection. Table 2 below summarizes the
approach volumes for the twelve highest hours of the day.
Table 2 – Carroll Avenue at Lakewood Drive Approach Volumes
Hour/Time Approaches
NB EB SB WB
1 7:00 AM 739 27 726 -
2 8:00 AM 739 31 820 -
3 9:00 AM 589 19 732 -
4 10:00 AM 586 25 720 -
5 11:00 AM 716 24 863 -
6 12:00 PM 887 36 1032 -
7 1:00 PM 990 37 836 -
8 2:00 PM 920 35 808 -
9 3:00 PM 880 29 951 -
10 4:00 PM 839 36 984 -
11 5:00 PM 828 42 1018 -
12 6:00 PM 845 30 857 -
Warrant 1 – Eight-Hour Vehicle Volume
Warrant 1 is broken down into two sub categories, condition A (minimum vehicular volume) and
condition B (interruption of continuous traffic). The standard indicates that the warrant is met if
either condition A or B is met for any eight hours on an average day.
Condition A
From Table 4C-1 in the TxMUTCD, with two or more lanes on the major approach and two or
more lanes on the minor approach, the threshold of volumes for Condition A is as follows:
• Major: 600 vehicles per hour (combined total of both approaches)
• Minor: 200 vehicles per hour (higher volume approach)
Based on the data shown in Table 2, these thresholds are not exceeded during any of the one-
hour periods at the study intersection. Condition A is not met.
Condition B
From Table 4C-1 in the TxMUTCD, with two or more lanes on the major approach and two or
more lanes on the minor approach, the threshold of volumes for Condition B is as follows:
• Major: 900 vehicles per hour (combined total of both approaches)
• Minor: 100 vehicles per hour (higher volume approach)
North Carroll 114 Properties, LLC
Queuing and Signal Warrant Study
- 6 -
Based on the traffic data in Table 2, these thresholds are not exceeded during any one-hour
period at the study intersection. Condition B is not met.
The TxMUTCD allows for a combination of Condition A and B with a reduced threshold of 80
percent. For Condition A the thresholds would be 480 vehicles per hour (both directions
combined) on the major street and 160 per hour at the highest minor street approach. The
thresholds for Condition B would be 720 vehicles per hour on the major street and 80 vehicles
per hour on the minor street approach.
Based on these criteria, not one of the one-hour periods meet or exceed the threshold for
Condition A nor Condition B. Neither Condition A or B are met, therefore Warrant 1 is not met
at this time.
Warrant 2 – Four-Hour Vehicle Volume
The standard for the four-hour vehicle volume warrant is met if the plotted points representing
the vehicles per hour on the major street (total of both approaches) and the vehicles per hour of
the higher volume minor street approach all fall above the applicable curve in Figure 5 (Figure
4C-1 from the TxMUTCD) shown below.
Figure 5 – Plotted Four-Hour Volumes
Based on the data shown in the graph above, none of the plotted points are above the threshold
curve for “two or more lanes and two or more lanes;” therefore, Warrant 2 is not met.
North Carroll 114 Properties, LLC
Queuing and Signal Warrant Study
- 7 -
Warrant 3 – Peak Hour
From the TxMUTCD:
The Peak Hour signal warrant is intended for use at a location where traffic conditions are such
that for a minimum of 1 hour of an average day, the minor-street traffic suffers undue delay
when entering or crossing the major street,
The need for a traffic control signal shall be considered if an engineering study finds that the
criteria in either of the following two categories are met:
A. The peak hour warrant is met if all three of the following conditions exist for the same one
hour (any four consecutive 15-minute periods) of an average day:
1. The total stopped time delay experienced by the traffic on one minor-street approach (one
direction only) controlled by a STOP sign equals or exceeds: 4 vehicle-hours for a one-
lane approach; or 5 vehicle-hours for a two-lane approach, and
2. The volume on the same minor-street approach (one direction only) equals or exceeds 100
vehicles per hour for one moving lane of traffic or 150 vehicles per hour for two moving
lanes, and
3. The total entering volume serviced during the hour equals or exceeds 650 vehicles per hour
for intersections with three approaches or 800 vehicles per hour for intersections with four
or more approaches.
B. The plotted point representing the vehicles per hour on the major street (total of both
approaches) and the corresponding vehicles per hour on the higher-volume minor-street
approach (one direction only) for 1 hour (any four consecutive 15-minute periods) of an
average day falls above the applicable curve in Figure 4C-3 for the existing combination of
approach lanes.
In examining the requirements of Category A, the highest approach volume on the minor street
(Lakewood Drive) was 42 vehicles per hour. This does not exceed the requirement in A2 of 150
vehicles per hour. Therefore, the conditions of Category A are not met and Warrant 3 is not met.
Warrant 8 – Roadway Network
This warrant examines the need for a signal as a way to improve organization of traffic flow on
the roadway network. This warrant is met if the study intersection meets the requirement of having
an entering volume of at least 1,000 vehicles per hour during the peak hour and has 5-year
projected volumes that meet one or more of Warrants 1, 2 or 3. While the study intersection does
have over 1,000 vehicles entering during the peak hour, it is not projected to meet any of Warrants
1, 2 or 3 in the next 5 years. For this to occur, the traffic volumes on Lakewood Drive would need
to triple (25 percent annual growth rate) to even come close to meeting the requirements for
Warrant 3 (Peak-Hour Warrant).
North Carroll 114 Properties, LLC
Queuing and Signal Warrant Study
- 8 -
Summary
Based on the analyses presented in the memorandum above, the relocation of the development
driveway to Lakewood Drive does not appear to significantly impact the queues on the eastbound
approach (Lakewood Drive) at the intersection of Carroll Avenue and Lakewood Drive. It is noted
that there is a small increase in the 95 th percentile queue in the PM peak hour due to the additional
projected trips related to the proposed increase in office space. But, the overall max queue (slightly
over one vehicle in length) remains well within normal parameters for a two-way stop-controlled
intersection on a major thoroughfare.
Based on a review of the Signal Warrants as contained in the TMUTCD, the intersection of Carroll
Avenue and Lakewood Drive does not meet any of the signal warrants, nor is it projected to meet
any Warrant within the next five (5) years.