Item 7C - Harborchase of Southlake TIA 2013-12-23Harborchase of Southlake
Southlake, Texas
Traffic Engineering Study
12/23/2013
SAVANT G ROU P
1700 Pacific Avenue, Suite 1240
Dallas, TX 75201
214.468.8200
TBPE Firm Registration # 10286
12/23/2013
Engineer -in -Charge:
* , Josh Smith P.E., PTOE
* J�
JOSHUA D. SMITH
'�......... /......................./
Under contract with:
��\ S8/0N*ZiN' \7 Pacheco Koch
TABLE OF CONTENTS
Introduction.................................................................................................................................................. 1
DataCollection..........................................................................................................................................3
RoadwayNetwork.....................................................................................................................................3
Analysis.........................................................................................................................................................4
AnalysisMethodology...............................................................................................................................4
2015 Future Background Traffic...............................................................................................................4
TripGeneration.........................................................................................................................................6
Trip Distribution and Assignment.............................................................................................................6
CapacityAnalysis.......................................................................................................................................
7
IntersectionSight Distance...........................................................................................................................
9
AuxiliaryLane Analysis................................................................................................................................
10
DrivewaySpacing Analysis..........................................................................................................................
11
Conclusions.................................................................................................................................................
11
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LIST OF TABLES
Table 1—
Intersection Level of Service Thresholds.......................................................................................4
Table 2
— 2015 Background Traffic Capacity Analysis...................................................................................
6
Table3
— Site Trip Generation......................................................................................................................
6
Table 4
— Existing Plus Project Capacity Analysis..........................................................................................
9
Table 5
— Intersection Sight Distance Analysis............................................................................................
10
Table 6
—Auxiliary Lane Volume Thresholds..............................................................................................10
Table 7
— Other State Highways Connection Spacing Criteria....................................................................
11
LIST OF FIGURES
Figure1
—Site Map....................................................................................................................................... 1
Figure2
—Site Plan........................................................................................................................................ 2
Figure3
—AM Background Traffic................................................................................................................. 5
Figure4
— PM Background Traffic................................................................................................................. 5
Figure5
—Trip Distribution........................................................................................................................... 7
Figure 6
— Projected 2015 AM Traffic
........................................................................................................... 8
Figure 7
— Projected 2015 PM Traffic
............................................................................................................ 8
Figure8
— Driveway Spacing....................................................................................................................... 11
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INTRODUCTION
Savant Group Inc. (SGI) was retained to complete a traffic engineering study for a proposed
assisted living facility. The proposed site is bordered by W. Southlake Boulevard on the south
N. Shady Oaks Drive on the east, an existing development on the southeast, and the proposed
Glenmore residential development and its entrance roads on the north and west, as shown in
Figure 1.
FIGURE 1 —SITE MAP
Aerial Image Source: Google Earth, http://mops.google.com
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The site plan is shown in Figure 2.The proposed assisted living facility will have 141 total beds
and two points of access. The access point from N. Shady Oaks Drive will allow all movements,
while the driveway on W. Southlake Boulevard will allow only right turns due to the presence of
an existing median and left turn storage bay for the adjacent intersection at Timber Lake Place.
The expected completion date for the project is 2015.
FIGURE 2 - SITE PLAN
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The analysis was designed to meet the requirements of the Texas Department of
Transportation (TxDOT), as the developer has already demonstrated to the City of Southlake
that minimum thresholds for requiring a traffic impact analysis under the City's guidelines will
not be met by the relatively small scale of the development. The analysis was also prepared so
as to be in accordance with the guidelines from the Institute of Transportation Engineers. The
study presents the expected trip generation from the site, presents the trip distribution and
route assignment of the expected traffic, and determines the necessary intersection geometry.
The following steps were executed to complete the analysis:
❖ Collection of traffic data, both daily and during peak hours at intersections and roadway
links in the study area.
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••• Field visit
❖ Forecasting of future "background" growth in traffic volumes anticipated without the
subject development for baseline comparison. This is estimated by examining recent
trends in traffic volume growth in the vicinity and estimating an annual percent growth
rate to account for yet -to -be determined adjacent developments and/or developments
too far away from the study site to warrant individual study.
❖ Addition of background trips from the study for the adjacent Glenmore residential
development, which is proposed by others;
❖ Analysis of the resulting background conditions for the horizon years when the subject
site is proposed to be completely built;
❖ Estimation of traffic generated from the proposed development;
❖ Distribution of traffic from the proposed development onto the existing roadway system
to each of several destination zones outside the study area;
❖ Intersection Capacity Analysis using Highway Capacity Manual methods;
❖ Intersection sight distance analysis;
❖ Auxiliary lane analysis; and
❖ Turn lane analysis.
DATA COLLECTION
Based on the location of the site and TxDOT requirements, it was determined to study the
following intersections that provide access to the proposed development:
❖ W. Southlake Boulevard (FM 1709) at Site Driveway (unsignalized);
❖ N. Shady Oaks Drive at Site Driveway (unsignalized); and,
❖ W. Southlake Boulevard (FM 1709 at N. Shady Oaks Drive (signalized).
Turning movement counts were collected on Tuesday, December 3, 2013 at the signalized
intersection. The raw data is included in Appendix A. Signal timing data was obtained from
Tx D OT.
A site visit was performed to inventory the existing conditions. The engineer conducting the
site visit collected intersection data from the study intersection including roadway geometry,
traffic control elements, and any other roadway elements that may impact the study network.
ROADWAY NETWORK
W. Southlake Boulevard is a six -lane divided roadway with a posted speed limit of 45 mph. It
connects to the City of Keller and I-35W to the west and to SH 114 and the City of Grapevine to
the east. The land uses along W. Southlake Boulevard are primarily commercial and residential.
N. Shady Oaks Drive is a two-lane undivided roadway. The land uses along N. Shady Oaks Drive
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are primarily residential. N. Shady Oaks Drive provides access to the City of Southlake's
Bicentennial Park and to the Don T. Durham Intermediate School.
ANALYSIS
ANALYSIS METHODOLOGY
SynchroT" version 7 was used to create a model of the existing roadway and perform capacity
analyses of the study intersection. The capacity analysis software in SynchroT" is based on the
Transportation Research Board's Highway Capacity Manual (HCM), 2000. The HCM is a
nationally recognized standard for performing capacity analyses.
Capacity analyses are evaluated based on a level of service that ranges from A (excellent) to F
(poor). Levels of service A through D are generally considered acceptable and levels of service E
and F are considered unacceptable. The level of service thresholds in the Highway Capacity
Manual for signalized intersections and STOP controlled intersections are shown in Table 1.
TABLE 1 - INTERSECTION LEVEL OF SERVICE THRESHOLDS
Control Delay Per Vehicle (seconds)
LOS
STOP Controlled
Signalized Intersection
Intersection
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
Generating traffic for proposed developments is typically based on information in the Li�p
Generation, 9t" Edition, 2012 and the Trip Generation Handbook, 2"d Edition, 2004, developed
by the Institute of Transportation Engineers (ITE). The rates and equations in these reports
were applied to the development to determine the anticipated trips generated from the
development where applicable.
2015 FUTURE BACKGROUND TRAFFIC
The software SynchroT" was used to analyze the study intersections with 2015 background
traffic with a 2% yearly growth rate. Included in the 2015 background traffic volumes was the
proposed Glenmore housing development near the project site. Figures 3 and 4 summarize the
lane configurations and volumes used in the model for the AM and PM peak hours,
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respectively. The results of the analyses are shown in the Table 2. Synchro'' reports for each
intersection can be found in Appendix B.
FIGURE 3 - AM BACKGROUND TRAFFIC
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FIGURE 4 - PM BACKGROUND TRAFFIC
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Southlake Blvd
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TABLE 2 — 2015 BACKGROUND TRAFFIC CAPACITY ANALYSIS
Control LOS
Case No. Intersection Type Approach AM Peak Hour
_ Approach Overall E
W. Southlake Blvd NB D
1 at N. Shady Oaks Si Traffic SB D nal EB C B
Dr g
WB A
PM Peak Hour
oroach I Overall
7
0
P]
As can be seen from the table above, W. Southlake Boulevard at N. Shady Oaks Drive will
operate at a LOS D or better during both the AM and PM peak hours.
TRIP GENERATION
For this analysis, land use code 254 (Assisted Living) was applied based off of the total beds in
the proposed development. The rates found using the Trip Generation Manual are shown in
Table 3. The analysis is included in Appendix C.
TABLE 3 — SITE TRIP GENERATION
ITE Land Use Intensity
Code (Occupied Beds)
254 Assisted Living 141
TRIP DISTRIBUTION AND ASSIGNMENT
Weekday AM Peak Hour PM Peak Hour
Trips In Out In Out
359 17 8 21 20
Once the total trips generated from the site were determined, the trips were distributed to the
surrounding roads and assigned to the two driveways. The traffic assignment was based on
existing traffic data and engineering judgment. The distribution used for the study is shown in
Figure 5.
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FIGURE 5 -TRIP DISTRIBUTION
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W 5outhlake Blvd
40% 1 < > 55%
CAPACITY ANALYSIS
SynchroT" was used to analyze each study intersection with its projected traffic. Figures 6 and 7
summarize the lane configurations and volumes used in the model for the AM and PM peak
hours, respectively. The results of the analyses are shown in the Table 4. SynchroT' reports for
each intersection can be found in Appendix D.
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FIGURE 6 - PROJECTED 2015 AM TRAFFIC
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FIGURE 7 - PROJECTED 2015 PM TRAFFIC
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TABLE 4 — EXISTING PLUS PROJECT CAPACITY ANALYSIS
LOS
Case No.
Intersection ControlType
W. Southlake Blvd Traffic
at N. Shady Oaks Signal
Dr g
Approach
AM Peak
Hour
PM Peak
Hour
Approach
Overall
Approach
Overall
1
NB
D
D
C
C
C
D
SB
D
EB
B
WB
E
Southlake
Boulevard at Side Street
Driveway Stop
N. Shady Oaks Dr Side Street
at Driveway Stop
A
2
SB
A
*
C
B
C
EB
*
WB
3
NB
*
A
A
A
SB
*
EB
B
*Approach does not have any traffic control and is assumed to operate without delay.
As can be seen from the table above, W. Southlake Boulevard at N. Shady Oaks Drive will
operate at a LOS D or better during both the AM and PM peak hours. Both driveways will
operate with minimal delay; therefore, improvements are not recommended.
INTERSECTION SIGHT DISTANCE
A roadway sight distance analysis was conducted at the existing south entrance on December
12, 2013. The available sight distance was compared with the recommended intersection sight
distances provided in American Association of State Highways and Transportation Officials
(AASHTO) roadway design guide "A Policy on Geometric Design of Highways and Streets". N.
Shady Oaks Drive has a posted speed limit of 30 mph and W. Southlake Boulevard has a posted
speed limit of 45 mph. The results of the analysis are shown in Table 5.
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TABLE 5 — INTERSECTION SIGHT DISTANCE ANALYSIS
Intersection Sight Distance Measurements
Right Turn Left Turn
ISD I ISD
AASHTO Requirement: >290 ft >335 ft Acceptable
30 MPH ISD?
N. Shady Oaks Drive >350 ft >500 ft Yes
Driveway
AASHTO Requirement: >430 ft N A Acceptable
45 MPH / ISD?
W. Southlake Boulevard I >500 ft I N/A I Yes
Driveway
As seen from Table 5 above, the available sight distance meets the minimum intersection sight
distance required by AASHTO at both driveways.
AUXILIARY LANE ANALYSIS
The Texas Department of Transportation Access Management Manual (Revised July 2011)
provides direction on volume thresholds for identifying when acceleration and deceleration
lanes along state routes should be considered. Chapter 2, Section 7 of the manual provides
criteria associated with auxiliary lanes on state routes. The information in Table 6 summarizes
volume thresholds for consideration of acceleration and deceleration lanes for each of the
development access points.
TABLE 6 — AUXILIARY LANE VOLUME THRESHOLDS
Right
Turn to or from Property (545 MPH)
Acceleration
Deceleration
Deceleration
Lane
Lane
Acceleration
Lane Required
Lane
TxDOT Requirement
>200 vph
> 60 vph
Required
W. Southlake
Boulevard Driveway
8
9
No
No
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As shown in Table 6, the maximum number of right turns to or from the property does not
exceed the minimum threshold requiring an auxiliary lane.
DRIVEWAY SPACING ANALYSIS
The Texas Department of Transportation Access Management Manual (Revised July 2011)
provides direction on minimum connection spacing. Chapter 2, Section 3 of the manual
provides criteria associated with spacing on other state highways. The information in Table 7
summarizes distance threshold for consideration of driveway spacing.
TABLE 7 - OTHER STATE HIGHWAYS CONNECTION SPACING CRITERIA
Distance
Current
Posted Speed
Required (ft)
Distance (ft)
45
360
322
FIGURE 8 - DRIVEWAY SPACING
FUTURE
GLENMORE HARBOR CHASE
SUBDIVISION i AT EXISTING
SOUTH LAKE n DEVELOPMENT
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T n«m.r v uc omK
SOU77HLAKE BOULEVAiiD
As shown in Figure 8, the distance between the proposed driveway and current driveways is
322 feet. The proposed driveway does not currently meet the required distance required by
Access Management Manual. The driveway currently splits the distance on either side equally.
The minor deficiency of 38 feet on each side is reasonable given the very low volume of turning
traffic anticipated at the subject site driveway.
CONCLUSIONS
An assisted living facility with two access points, one on each W. Southlake Boulevard and
another on N. Shady Oaks Drive, is the proposed development slated for completion in 2015.
The intersection of W. Southlake Boulevard at N. Shady Oaks Drive will continue to operate at a
LOS D or better after traffic from the proposed development is added to the roadway network.
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This analysis did not find a need for either a deceleration or acceleration lane on W. Southlake
Boulevard. The proposed locations of the driveways will provide sufficient sight distance.
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