Item 8 - Traffic Study & Turn ExhibitMEMORANDUM
To:Jody Alumbaugh, PE
President – Willowtree Custom Homes
From: Douglas M Arnold, P.E.
Kimley-Horn and Associates, Inc.
Date: December 11, 2023
Re:Traffic Study
Proposed Residential and Office Development
Southlake, Texas
PURPOSE
This memorandum serves as a traffic study for a proposed single-family and office development located
on the west side of North Carroll Avenue, north of Southlake Boulevard, in the City of Southlake, Texas.
The development is anticipated to include 28 detached single-family dwelling units and 26,000 square
feet of general office space.Exhibit 1 (attached) provides the general site location of the proposed
development.
The following traffic assessment will include the following: existing and proposed roadway
characteristics, proposed development characteristics, need for auxiliary lanes, access spacing, sight
distance, and driveway intersection delay and level of service (LOS).
EXISTING TRANSPORTATION SYSTEM
North Carroll Avenue is a four-lane divided Arterial roadway with a posted speed of 30 mph. North
Carrol Avenue provides access for development traffic to Southlake Boulevard (FM 1709) to the south
and SH 114 to the north. Adjacent to the development, there is a raised median along North Carroll
Avenue. This section of North Carroll Avenue is built out to its ultimate cross section.
Southlake Boulevard (FM 1709) is a six-lane divided Arterial with a posted speed of 45 mph.
Southlake Boulevard provides access to Kimball Avenue and SH 114 to the east, and other City
thoroughfares to the west.
Based on recent (2019) TxDOT traffic count data, the daily volumes along North Carroll Avenue, north
of Southlake Boulevard, is approximately 19,900 vehicles per day. The peak hour volumes along North
Carroll Avenue in 2019 were 1,530 vehicles during the AM peak hour (841 NB, 689 SB) and 1,830
vehicles during the PM peak hour (795 NB, 1,035 SB).
PROPOSED DEVELOPMENT INFORMATION
The proposed development sits on a undeveloped plot and as such generates no traffic. The
development’s concept plan (attached) includes 28 single-family detached housing dwellings and a +/-
26,000 square-foot general office building.
12/11/2023
Page 2
Site Access
As previously mentioned, the subject property is located on the west side of North Carroll Avenue. To
the north of the development, there is a developed residential neighborhood, and to the south is an
undeveloped parcel and an existing medical office building, both under separate ownership. West of
the subject property is a residential neighborhood; based on feedback from the neighborhood and City
staff, no connections are proposed from this development to that neighborhood via Cross Lane (other
than a gated emergency access point). Furthermore, there are no existing easements along the
southern property line for any potential cross access connections. With that said, all access to the site
must be provided via North Carroll Avenue.
Based on the development concept plan, there are two driveways proposed to serve the development.
The southern driveway, located approximately 600 feet north of Southlake Boulevard, will primarily
serve the general office development. The northern driveway, located approximately 180 feet north of
the southern driveway and approximately 350 feet south of Ownby Lane, will primarily serve the
residential homes.
Since there is a raised median along North Carroll Avenue spanning the entire frontage of the subject
property, and access to Cross Lane is for emergency access only, the development is proposed to
install a northbound left-turn lane to serve the northern site driveway. An analysis of this proposed
improvement will be provided later in the memo. The developer is looking to get conceptual approval
of the left-turn lane as part of this traffic study, with engineering plans to come shortly after as the
project moves forward.
Trip Generation
Based on trip generation rates from the 11th edition of the ITE Trip Generation Manual for Single Family
Detached Homes (ITE Land Use Code 210) and General Office (ITE Land Use Code 710),the site is
anticipated to generate 60 AM peak hour driveway trips and 63 PM peak hour driveway trips. A
breakdown of the trip generation is provided in Table 1. No internal capture was assumed between the
residential and general office land uses.
Table 1: Trip Generation Analysis
Trip Distribution and Assignment
It is anticipated that the site traffic will be distributed to North Carrol Avenue and Southlake Boulevard
accordingly: 30% to/from the west on Southlake Boulevard, 25% to/from the east on Southlake
Boulevard, 30% to/from the north on North Carrol Avenue, and 15% to/from the south on North Carroll
Avenue.Exhibit 2 (attached) provides the anticipated trip distribution at the two (2) project driveways
and one (1) study intersection.Exhibit 3 provides the anticipated trip assignment at the driveways.
Based on the trip assignment values, the increase in traffic along North Carroll Avenue as a result of
this proposed developments equates to less than a 2.0% increase between Southlake Boulevard and
the site and less than 1% north of the site.
In Out Total In Out Total
Single-Family Detached Housing 210 28 Dwelling Units 264 5 15 20 16 10 26
General Office 710 26,000 SF 282 35 5 40 6 31 37
546 40 20 60 22 41 63TOTAL SITE TRAFFIC
Daily AM Peak Hour PM Peak HourLand Use Description ITE
Code
Intensity /
Units
Page 3
DRIVEWAY CAPACITY ANALYSIS
A capacity analysis was performed for the project driveways along North Carroll Avenue. Capacity
analysis results are listed in terms vehicle delay and level of service (LOS). LOS is a qualitative term
describing operating conditions (vehicle delay) a driver will experience while traveling on a specific
street or highway during a specific time interval. It ranges from A (very little delay) to F (longer delays
and congestion). TxDOT considers LOS D or better to be the target LOS for design and evaluation
purposes. Average total delay ranges of each operational state for intersections, based on the Highway
Capacity Manual (HCM) 6th Edition, are presented in Table 2.
Table 2: Level of Service Definitions
Level of Service Signalized Intersection
Average Total Delay (sec/veh)
Unsignalized Intersection
Average Total Delay (sec/veh)
A ≤10 <10
B >10 and ≤20 >10 and <15
C >20 and ≤35 >15 and <25
D >35 and ≤55 >25 and <35
E >55 and ≤80 >35 and <50
F >80 >50
The capacity analysis was performed using Synchro, which is an intersection analysis software based
on the Highway Capacity Manual (HCM). The traffic volumes used for the analysis are the combination
of the 2019 peak hour volumes provided by TxDOT, grown by 8% to account for growth in traffic
between 2019 and 2023 at 2% annually, and the site traffic volumes from Exhibit 2. As previously
discussed, a northbound left-turn lane is proposed at the northern site driveway.
Table 3 summarizes the intersection operation results for the three scenarios during the weekday AM
and PM peak hours. The delay and LOS were reported for the stop-controlled eastbound movement at
both driveways as well as the northbound left-turn movement at the northern driveways. Based on the
analysis, all movements are anticipated to operate at LOS B or better during both the AM and PM peak
hours. The Synchro 11TM output sheets for analyses are included in Attachment D.
Table 3: Level of Service Summary
Due to the low number of right-turn volumes into the project driveways, right-turn deceleration lanes
are not recommended. The analysis further supports this as the southbound through movement is
anticipated to operate at LOS A at both project driveways during the AM and PM peak hours.
Delay
(sec/veh)LOS Delay
(sec/veh)Total
EBR 11.3 B 13.7 B
NBL 9.7 A 11.5 B
North Carroll Avenue & Southern Driveway EBR 11.2 B 13.8 B
North Carroll Avenue & Northern Driveway
Intersection Movement
AM Peak Hour PM Peak Hour
Page 4
CONCLUSION AND RECOMMENDATIONS
A traffic study was performed for a residential and office development located on the west side of North
Carroll Avenue, north of Southlake Boulevard, in the City of Southlake, Texas.
The following conclusions can be made from the analysis:
· The development is anticipated to include 28 single-family dwelling units and 26,000 square
feet of general office space. The development represents less than a 2.0% increase in overall
traffic volumes along North Carroll Avenue.
· The development is anticipated to have two driveways accessing North Carroll Avenue; the
northern driveway is anticipated to provide ingress and egress movements (left-turn egress
prohibited) and the southern driveway is anticipated to provide ingress and egress movements
(right-in and right-out only).
· In order to provide ingress from the south, which is anticipated to comprise of 70% of the total
entering site traffic, a northbound left-turn lane is proposed at the northern site driveway. The
left-turn lane would be designed similar to the existing southbound left-turn lane at Main Street,
which has a similar width median. The southbound queues at Southlake Boulevard are not
anticipated to impact the proposed northbound left-turn lane operations.
·All traffic movements at the driveway connections are anticipated to operate at LOS B or better
for during the AM and PM peak hours. The northbound left-turn movement from the proposed
left-turn lane is anticipated to operate at LOS B with less than one vehicle queue during both
the AM and PM peak hours.
·The City has recommended a residential only gate on the southwestern part of the property to
connect with Tower Road. There are currently no existing easements in place to accommodate
this connection. While recognizing that this additional residential connection could distribute
site traffic further to Southlake Boulevard, the analysis shows that the proposed connections
to North Carroll Avenue are sufficient to provide acceptable LOS, and no other site connections
are needed. As stated above, the development represents less than a 2.0% increase in overall
traffic volumes along North Carroll Avenue.
Page 5
ATTACHMENTS
Exhibit 1: Site Location Map
15%15%
(50%)
70%(30%)
15% (50%)
(50%)
70%
(30%)
(70%) (30%)
70%
25%
(30%) (15%) (25%)
30%
15%
LEGEND:
X (Y)
X = AM Peak Hour Turning Movements
Y = PM Peak Hour Turning Movements
Volumes may not sum from point to point due to rounding
and presence of smaller driveways not included in analysis.
EXHIBIT 2
TRIP DISTRIBUTION
N
NOT TO SCALE
WILLOWTREE
E SOUTHLAKE BLVD
SITE NCARROLLAVE30%25%
15%
30%
MAIN STREET
6 6
(3)(3)
10 (21)
28 6
(15)(12)
6 10
(3)(21)
10 (21)
14 0 6
(29)(0)(12)
28 0
(15)(0)
LEGEND:
X (Y)
X = AM Peak Hour Turning Movements
Y = PM Peak Hour Turning Movements
Volumes may not sum from point to point due to rounding
and presence of smaller driveways not included in analysis.
EXHIBIT 3
TRIP ASSIGNMENT
N
NOT TO SCALE
WILLOWTREE
E SOUTHLAKE BLVD NCARROLLAVESITE
AM: 18 veh
PM: 19 veh
AM: 15 veh
PM: 16 veh
AM: 9 veh
PM: 9 veh
AM: 18 veh
PM: 18 veh
MAIN STREET
HCM 6th TWSC Build-Out AM Peak Hour
1: N Carroll Ave. & Northern Driveway
Synchro 11 Report
Intersection
Int Delay, s/veh 0.2
Movement EBL EBR NBL NBT SBT SBR
Lane Configurations
Traffic Vol, veh/h 0 10 28 908 757 6
Future Vol, veh/h 0 10 28 908 757 6
Conflicting Peds, #/hr 0 0 0 0 0 0
Sign Control Stop Stop Free Free Free Free
RT Channelized - None - None - None
Storage Length -0 100 ---
Veh in Median Storage, # 0 --0 0 -
Grade, %0 --0 0 -
Peak Hour Factor 92 92 92 92 92 92
Heavy Vehicles, %2 2 2 2 2 2
Mvmt Flow 0 11 30 987 823 7
Major/Minor Minor2 Major1 Major2
Conflicting Flow All - 415 830 0 -0
Stage 1 ------
Stage 2 ------
Critical Hdwy - 6.94 4.14 ---
Critical Hdwy Stg 1 ------
Critical Hdwy Stg 2 ------
Follow-up Hdwy - 3.32 2.22 ---
Pot Cap-1 Maneuver 0 586 798 ---
Stage 1 0 -----
Stage 2 0 -----
Platoon blocked, %---
Mov Cap-1 Maneuver - 586 798 ---
Mov Cap-2 Maneuver ------
Stage 1 ------
Stage 2 ------
Approach EB NB SB
HCM Control Delay, s 11.3 0.3 0
HCM LOS B
Minor Lane/Major Mvmt NBL NBTEBLn1 SBT SBR
Capacity (veh/h)798 - 586 --
HCM Lane V/C Ratio 0.038 - 0.019 --
HCM Control Delay (s)9.7 - 11.3 --
HCM Lane LOS A -B --
HCM 95th %tile Q(veh)0.1 - 0.1 --
HCM 6th TWSC Build-Out AM Peak Hour
2: N Carroll Ave. & Southern Driveway
Synchro 11 Report
Intersection
Int Delay, s/veh 0.1
Movement EBL EBR NBL NBT SBT SBR
Lane Configurations
Traffic Vol, veh/h 0 10 0 936 761 6
Future Vol, veh/h 0 10 0 936 761 6
Conflicting Peds, #/hr 0 0 0 0 0 0
Sign Control Stop Stop Free Free Free Free
RT Channelized - None - None - None
Storage Length -0 ----
Veh in Median Storage, # 0 --0 0 -
Grade, %0 --0 0 -
Peak Hour Factor 92 92 92 92 92 92
Heavy Vehicles, %2 2 2 2 2 2
Mvmt Flow 0 11 0 1017 827 7
Major/Minor Minor2 Major1 Major2
Conflicting Flow All - 417 -0 -0
Stage 1 ------
Stage 2 ------
Critical Hdwy - 6.94 ----
Critical Hdwy Stg 1 ------
Critical Hdwy Stg 2 ------
Follow-up Hdwy - 3.32 ----
Pot Cap-1 Maneuver 0 585 0 ---
Stage 1 0 -0 ---
Stage 2 0 -0 ---
Platoon blocked, %---
Mov Cap-1 Maneuver - 585 ----
Mov Cap-2 Maneuver ------
Stage 1 ------
Stage 2 ------
Approach EB NB SB
HCM Control Delay, s 11.3 0 0
HCM LOS B
Minor Lane/Major Mvmt NBTEBLn1 SBT SBR
Capacity (veh/h)- 585 --
HCM Lane V/C Ratio - 0.019 --
HCM Control Delay (s)- 11.3 --
HCM Lane LOS -B --
HCM 95th %tile Q(veh)- 0.1 --
HCM 6th TWSC Build-Out PM Peak Hour
1: N Carroll Ave. & Northern Driveway
Synchro 11 Report
Intersection
Int Delay, s/veh 0.2
Movement EBL EBR NBL NBT SBT SBR
Lane Configurations
Traffic Vol, veh/h 0 21 15 870 1121 3
Future Vol, veh/h 0 21 15 870 1121 3
Conflicting Peds, #/hr 0 0 0 0 0 0
Sign Control Stop Stop Free Free Free Free
RT Channelized - None - None - None
Storage Length -0 100 ---
Veh in Median Storage, # 0 --0 0 -
Grade, %0 --0 0 -
Peak Hour Factor 92 92 92 92 92 92
Heavy Vehicles, %2 2 2 2 2 2
Mvmt Flow 0 23 16 946 1218 3
Major/Minor Minor2 Major1 Major2
Conflicting Flow All - 611 1221 0 -0
Stage 1 ------
Stage 2 ------
Critical Hdwy - 6.94 4.14 ---
Critical Hdwy Stg 1 ------
Critical Hdwy Stg 2 ------
Follow-up Hdwy - 3.32 2.22 ---
Pot Cap-1 Maneuver 0 437 567 ---
Stage 1 0 -----
Stage 2 0 -----
Platoon blocked, %---
Mov Cap-1 Maneuver - 437 567 ---
Mov Cap-2 Maneuver ------
Stage 1 ------
Stage 2 ------
Approach EB NB SB
HCM Control Delay, s 13.7 0.2 0
HCM LOS B
Minor Lane/Major Mvmt NBL NBTEBLn1 SBT SBR
Capacity (veh/h)567 - 437 --
HCM Lane V/C Ratio 0.029 - 0.052 --
HCM Control Delay (s)11.5 - 13.7 --
HCM Lane LOS B -B --
HCM 95th %tile Q(veh)0.1 - 0.2 --
HCM 6th TWSC Build-Out PM Peak Hour
2: N Carroll Ave. & Southern Driveway
Synchro 11 Report
Intersection
Int Delay, s/veh 0.1
Movement EBL EBR NBL NBT SBT SBR
Lane Configurations
Traffic Vol, veh/h 0 21 0 885 1139 3
Future Vol, veh/h 0 21 0 885 1139 3
Conflicting Peds, #/hr 0 0 0 0 0 0
Sign Control Stop Stop Free Free Free Free
RT Channelized - None - None - None
Storage Length -0 ----
Veh in Median Storage, # 0 --0 0 -
Grade, %0 --0 0 -
Peak Hour Factor 92 92 92 92 92 92
Heavy Vehicles, %2 2 2 2 2 2
Mvmt Flow 0 23 0 962 1238 3
Major/Minor Minor2 Major1 Major2
Conflicting Flow All - 621 -0 -0
Stage 1 ------
Stage 2 ------
Critical Hdwy - 6.94 ----
Critical Hdwy Stg 1 ------
Critical Hdwy Stg 2 ------
Follow-up Hdwy - 3.32 ----
Pot Cap-1 Maneuver 0 430 0 ---
Stage 1 0 -0 ---
Stage 2 0 -0 ---
Platoon blocked, %---
Mov Cap-1 Maneuver - 430 ----
Mov Cap-2 Maneuver ------
Stage 1 ------
Stage 2 ------
Approach EB NB SB
HCM Control Delay, s 13.8 0 0
HCM LOS B
Minor Lane/Major Mvmt NBTEBLn1 SBT SBR
Capacity (veh/h)- 430 --
HCM Lane V/C Ratio - 0.053 --
HCM Control Delay (s)- 13.8 --
HCM Lane LOS -B --
HCM 95th %tile Q(veh)- 0.2 --