Item 6B BDI Traffic StudyTraffic Study
To Serve
Southlake Commons
FM 1709 and White Chapel Blvd.
Southlake, TX
February 19, 2017
Prepared By
BOYDSTON DESIGNS, INC.
Au� 222 W. Fxc6ange Ave., Suite 1 o5
Fort Worth, TX 7616+
Voice: 817 626-7878 - Fax: 817 626-7879
Civil Engineering -Surveying -Land Planning
E. Reg.# F-11307 • S. Reg.#10193818
Table of Contents
I.
Introduction
II.
Study Procedure and Methodology
III.
Existing Roadway Conditions
IV.
Future Roadway Conditions
V.
Existing Traffic Patterns
VI.
Proposed Land Uses and Estimated
Trip Generation
VII.
Distribution of Site -Generated Traffic
VIII.
Access Spacing on FM 1709
IX.
Deceleration Lanes along FM 1709
X.
Sight Distance along FM 1709
XI.
Recommendations to Improve Future
Traffic Conditions
XII.
Summary
XIII.
Supplemental Exhibits 1-3
Traffic Study Page 3
Southlake Commons in Southlake, Texas February 19, 2017
I. Introduction
Boydston Designs, Inc. (BDI) has prepared this study at the request of Conifer Real
Estate for the purpose of assessing traffic impact of the proposed Southlake
Commons development on FM 1709 (also known as Southlake Boulevard) and White
Chapel Blvd. in Southlake, Texas. A Traffic Impact Analysis and evaluation of
proposed improvements was prepared by Boydston Designs in 2010 and approved
by the City of Southlake. Improvements proposed in that study were constructed in
approximate conformance its recommendations and with the engineering plans
subsequently prepared by Boydston Designs.
Access to the Southlake Commons development is proposed to occur via an existing
right-in, right-out drive with deceleration lane onto FM 1709 (Driveway A), an existing
driveway from the First Financial Bank site onto White Chapel Blvd. (Driveway B), and
a common driveway adjacent to a median opening on White Chapel Blvd (Driveway
C). The locations of these driveways are illustrated in Figure 1 (p. 9).
A vicinity map depicting the Southlake Commons site (referred to as the Church
Property in the 2010 TIA) and the existing First Financial Bank is shown below.
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Traffic Study Page 4
Southlake Commons in Southlake, Texas February 19, 2017
II. Study Procedure and Methodology
This abbreviated Traffic Study has been prepared by Boydston Designs, Inc. (BDI) on
behalf of Conifer Real Estate for review by the City of Southlake. This study includes
trip generation estimates, directional distribution assignments that have been modified
somewhat from the previous traffic impact analysis, and a review of existing sight
distances at existing access points. Traffic simulations, level of service calculations,
estimation of intersection delays, and other more advanced intersection analyses
have not been performed.
The development under consideration consists of three mixed use retail buildings and
five mixed use office buildings. Table 1 lists the total floor areas of each anticipated
use category. The traffic from the existing First Financial Bank, which shares access
with the Southlake Commons development, is included in Table 2. Traffic estimates in
these tables have been rounded to the nearest whole number, which may result in
apparent discrepancies when comparing subcategories with total traffic estimates.
Trip generation for Southlake Commons has been determined based on anticipated
use data provided by the developer and in accordance with Trip Generation Manual,
9th Ed. and Trip Generation Handbook, 2nd Ed. published by the Institute of
Transportation Engineers (ITE). City -collected traffic counts have also been included
in this report for purposes of comparison.
III. Existing Roadway Conditions
The area of study is located south of FM 1709 and west of White Chapel Blvd. All
driveways referenced in this study currently exist, and no new ones are proposed at
this time. FM 1709 is a divided road with three lanes of travel each in the eastbound
and westbound directions with periodically spaced median openings for dedicated left
turn lanes. (At the time of the previous study, FM 1709 was an undivided
thoroughfare with a dedicated center left turn lane.) Dedicated right turn deceleration
lanes are present at the intersection of the driveway onto FM 1709 (Driveway A) and
with the intersection of FM 1709 and White Chapel Blvd. North of FM 1709, White
Chapel Blvd. is built to a five lane undivided standard, with two lanes each in the
northbound and southbound directions and a dedicated center left turn lane for a
distance of approximately 1,100 feet. South of FM 1709, White Chapel Blvd. is built
to a four lane divided standard with intermittent median breaks for deceleration and
left turn lanes for a distance of approximately 1,000 feet. A median is located at the
common driveway onto White Chapel Blvd (Driveway C). Beyond these distances,
White Chapel Blvd. is a two lane undivided road. The speed limit on FM 1709 is 45
mph. The speed limit on White Chapel Blvd is 40 mph north of FM 1709 and 30 mph
south of FM 1709.
Traffic Study
Southlake Commons in Southlake, Texas
IV. Future Roadway Conditions
Page 5
February 19, 2017
No proposed roadway improvements in the vicinity of this project are known. The
Southlake 2030 Comprehensive Plan does not indicate any thoroughfare
improvements for FM 1709 or White Chapel Blvd. adjacent to the Southlake
Commons development.
V. Existing Traffic Patterns
The City of Southlake collects traffic data for a number of key street locations. From
the 2015 traffic data published by the City of Southlake, two 24-hour traffic count
locations are potentially relevant to this study. The first is located on FM 1709 near
the intersection with White Chapel Blvd. (indicated as 17E and 17W in the city's
data). The second is located on White Chapel Blvd. and is located south of FM 1709
and north of Continental Blvd (indicated as 57N and 57S in city data).
FM1709
Eastbound: 27,182 vehicles
Westbound: 25,385 vehicles
Total: 52,567 vehicles
White Chapel Blvd.
Northbound: 4,434 vehicles
Southbound: 4,857 vehicles
Total: 9,291 vehicles
VI. Proposed Land Uses and Estimated Trip Generation
The land uses for the proposed Southlake Commons development are shown in
Table 1 on the following page. Trip generation for Southlake Commons has been
estimated based a breakdown of anticipated usage provided by the developer.
Traffic for the existing First Financial Bank was tabulated based on data provided by
First Financial Bank for the week of August 15 — August 19, 2016. The busiest day
during this interval was used as the basis of estimating the bank's daily traffic, and
allowance was made for thirteen employees in excess of the trips generated by bank
customers.
TABLE 1 - TRIP GENERATION CALCULATIONS
Base Trio Generation Data (oer 1000 sf
Use
ITE Code
Area SF
Weekday
AM Peak
In %
Out %
PM Peak
In %
Out %
Sat.
Sat. Peak
In %
Out %
Sun.
Sun. Peak
General Office
710
15,309
NA
NA
0.88
0.12
NA
0.17
0.83
NA
0.43
0.54
0.46
1.05
0.16
Medical Office
720
12,834
NA
2.39
0.79
0.21
NA
0.28
0.72
8.96
3.63
0.57
0.43
1.55
0.40
General Retail
820
9,447
NA
NA
0.62
0.38
NA
0.48
0.52
NA
NA
0.52
0.48
NA
3.12
High -Turnover Restaurant
932
6,810
127.15
10.81
0.55
0.45
9.85
0.60
0.40
158.37
14.07
0.53
0.47
131.84
18.46
Starbucks/Casual Dining
937
2,000
818.58
100.58
0.51
0.49
42.80
0.50
0.50
687.87
84.52
0.50
0.50
687.87
84.52
Entries listed as "NA" are calculated
with fitted curve equations provided in ITE
Trip Generation Totals
Use
ITE Code
Area SF
Weekday
AM Peak
AM In
AM Out
PM Peak
PM In
PM Out
Sat.
Sat. Peak
Sat.Pk. In
Sat.Pk. Out
Sun.
Sun. Peak
General Office
710
15,309
315
43
38
5
96
16
79
63
7
4
3
16
2
Medical Office
720
11,190
310
31
24
6
41
11
29
100
41
23
17
17
4
General Retail
820
9,447
1465
37
23
14
123
59
64
2090
189
98
91
152
29
High -Turnover Restaurant
932
6,810
866
74
40
33
67
40
27
1078
96
51
45
898
126
Starbucks/Casual Dining
937
2,000
1637
201
103
99
86
43
43
1376
169
85
85
1376
169
AM Peak
PM Peak
Sat. Peak
Weekday
AM Tot.
AM In
AM Out
PM Tot.
PM In
PM Out
Sat.
Sat. Tot.
Sat. In
Sat. Out
Sun.
Sun. Tot.
TRIP TOTALS
4,593
385
228
157
412
170
242
4,707
501
260
241
2,459
331
Traffic Study
Southlake Commons in Southlake, Texas
Page 7
February 19, 2017
Estimated trip generation on the existing bank site and the future Southlake
Commons development is shown in Table 2 below:
Table 2 - Projected Trip Generation for Study Area
Land Use
(Density)
AM Peak Hour of Adjacent
Street Traffic
PM Peak Hour of Adjacent
Street Traffic
24 -Hour
In Out Total
In Out Total Total
First Financial
Bank
30 20 50
15 25 40 250
8,100 sf (4 lanes)
Southlake
Commons
228 157 385
170 242 412 4,593
Table 1
The table above was developed based on Trip Generation Manual, 9t-" Ed., published
by the Institute of Transportation Engineers. Where fitted curve equations were
provided by ITE, these were used to estimate generated trips. Otherwise, best fit
linear regression data was used.
Traffic Study
Southlake Commons in Southlake, Texas
VII. Distribution of Site -Generated Traffic
Page 8
February 19, 2017
In preparing its 2010 Traffic Impact Analysis for First Financial Bank and the Church
Property, BDI assumed the following trip distributions:
To and from the East via FM 1709:
35%
To and from the West via FM 1709:
30%
To and from the South via White Chapel Blvd:
20%
To and from the North via White Chapel Blvd:
15%
INBOUND MOVEMENTS: It is assumed that 65% of traffic approaching Southlake
Commons from the east will turn left to use the driveways onto White Chapel Blvd.
(Driveways B and C), while the remaining 35% will utilize alternate routes (such as U-
turns on FM 1709) to access Southlake Commons via the driveway onto FM 1709
(Driveway A). Traffic approaching from the north is also assumed to utilize the
driveways onto White Chapel Blvd. (Driveways B and C). It is assumed that 60% of
traffic using a right turning movement to access the site from White Chapel Blvd. will
enter the First Financial Bank driveway (Driveway B) and that the remaining 40% will
utilize the common driveway (Driveway C). Traffic approaching from the South is
anticipated to enter the common driveway on White Chapel Blvd. (Driveway C) using
left turning movements. Traffic entering from the West was assigned to the FM 1709
driveway (Driveway A). Turning movements at this driveway are limited to right-in/out
movements because of the existing median. It is assumed that all traffic approaching
First Financial Bank from the north and east will access it via its dedicated driveway
onto White Chapel Blvd. (Driveway B), that traffic from the south will access First
Financial Bank via the common driveway onto White Chapel Blvd. (Driveway C), and
that traffic from the west will access it via the shared driveway onto FM 1709
(Driveway A).
OUTBOUND MOVEMENTS: It is assumed that all eastbound traffic will exit the site
using a right -out at the FM1709 driveway (Driveway A). Northbound traffic is
assigned to use a left -out at the Common White Chapel Drive (Driveway C). Half of
westbound traffic is also assigned to use a left -out at the Common White Chapel
Drive (Driveway C), with the remaining half utilizing a right -out at the FM1709
driveway (Driveway A), thereafter seeking alternate routes to return toward the West.
Southbound traffic leaving Southlake Commons is assumed to use the First Financial
Bank driveway (Driveway B) onto White Chapel and the Common White Chapel
Drive (Driveway C) in a 50/50 split. It is, however, assumed that all traffic from First
Financial Bank and departing to the South will exclusively use the First Financial
bank driveway onto White Chapel (Driveway B).
Traffic Study
Southlake Commons in Southlake, Texas
Page 9
February 19, 2017
Figures 1A and 1 B that follow (not to scale) show schematics of the existing driveway
locations as well as the percentages allocated to each driveway turning movement
and intersection movement for inbound and outbound traffic, respectively. Left -in and
left -out movements are possible only at the common driveway onto White Chapel
Blvd (Driveway C). Other drives are right -in, right -out only. The intersection
percentages shown are percentages of total site generated traffic passing through
the intersection via each listed turning movement. Since some site generated traffic
bypasses the intersection, the sum of listed percentages is less than 100%.
FIGURE 1A
Weekday Inbound Trip Percentage Distribution
Southlake Commons and
First Financial Bank
U 0 WBR
o�v �
I I � -"*— 11,79E WBT
FM 1709 �J i g f— 23.3X WBL
41.72—)
FM 1709 Driveway
(Driveway A)
First Financial Bank (FFA}
Driveway (Driveway B)
EBL 0 J
EBT 0 —�
EBR 0
Common Driveway—`
(Driveway C)
Traffic Study
Southlake Commons in Southlake, Texas
Page 10
February 19, 2017
FIGURE 1S
Weekday Outbound Trip Percentage Distribution
Southlake Commons and
First Financial Sank
'G
vlvv �
0 WBR
FM 1709 j 1 o W@L
®L 15.070
®T 35.0X —�
FM 1709 Driveway ®R 0—)
(DrNeway A)
10.591
First R-nandal Bank (FFB)
Driveway (Driveway B)
30.OX
Common Driveway--""
(Driveway C) 9.5%—)
-I f r
Traffic Study
Southlake Commons in Southlake, Texas
Page 11
February 19, 2017
Figure 2 below (not to scale) shows a schematic of the existing driveway locations as
well as estimated number of turning movements and intersection movements for the
AM and PM peak conditions. Expected AM turning movements are listed first,
followed by PM movements in parentheses.
FIGURE 2
AM (PM) Peak Hour Additional Trips
Southlake Commons and
First Financial Sank
ti
v -v
v a 0 (0) WBR
.1-M 1709 T (44) WBL
105 (78)- EBL 27 (40)
EBT 52 (94)
FM 1709 Driveway EBR 0(0)—)
(Driveway A)
m
First Financial Bank (FFB)20 (29y,
Driveway (Driveway B)
53 (80)
Common Drive way----"'
(Driveway C) 15 (24)
M
N
in
Zd~m%
z z z
Table 3 on the following page lists the resulting total turning movements of each type
for daily, AM Peak, and PM Peak conditions. Table 4 lists the intersection movement
totals and percentages.
TABLE 3 - DISTRIBUTION OF TURNING MOVEMENTS
Southlake Commons - Inbound movements
First Financial - Inbound movements
Allocation
Fraction
Movement
Fraction
Daily
AM Peak
PM Peak
Sat. Peak.
Right -In at FFB White Chapel Drive
0.2265
520
52
38
59
Right -In At Common White Chapel Drive
0.1510
347
34
26
39
Left -In At Common White Chapel Drive
0.2000
459
46
34
52
Right -In At FM1709 Driveway
0.4225
970
96
72
110
Total Inbound (Southlake Commons)
2297
228
170
260
First Financial - Inbound movements
TOTAL INBOUND MOVEMENTS
Movement
Right -In At FFB White Chapel Drive
Right -In At Common White Chapel Drive
Left -In At Common White Chapel Drive
Right -In At FM1709 Driveway
TOTAL SITE INBOUND
Southlake Commons - Outbound movements
Movement
Right -Out At FFB White Chapel Drive
Right -Out At Common White Chapel Drive
Left -Out At Common White Chapel Drive
Right -Out At FM1709 Driveway
Total Outbound (Southlake Commons)
First Financial - Outbound movements
Movement
Right -Out At FFB White Chapel Drive
Right -Out At Common White Chapel Drive
Left -Out At Common White Chapel Drive
Right -Out At FM1709 Driveway
Total Outbound (First Financial Bank)
TOTAL OUTBOUND MOVEMENTS
Movement
Right -Out At FFB White Chapel Drive
Right -Out At Common White Chapel Drive
Left -Out At Common White Chapel Drive
Right -Out At FM1709 Driveway
TOTAL SITE OUTBOUND
TOTAL TRIPS
Allocation
Allocation
Fraction
Movement
Fraction
Daily
AM Peak
PM Peak
Sat. Peak
Right -In at FFB White Chapel Drive
0.500
63
15
8
10
Right -In At Common White Chapel Drive
0.000
0
0
0
0
Left -In At Common White Chapel Drive
0.200
25
6
3
6
Right -In At FM1709 Driveway
0.300
38
9
5
6
Total Inbound (First Financial Bank)
125
30
15
22
TOTAL INBOUND MOVEMENTS
Movement
Right -In At FFB White Chapel Drive
Right -In At Common White Chapel Drive
Left -In At Common White Chapel Drive
Right -In At FM1709 Driveway
TOTAL SITE INBOUND
Southlake Commons - Outbound movements
Movement
Right -Out At FFB White Chapel Drive
Right -Out At Common White Chapel Drive
Left -Out At Common White Chapel Drive
Right -Out At FM1709 Driveway
Total Outbound (Southlake Commons)
First Financial - Outbound movements
Movement
Right -Out At FFB White Chapel Drive
Right -Out At Common White Chapel Drive
Left -Out At Common White Chapel Drive
Right -Out At FM1709 Driveway
Total Outbound (First Financial Bank)
TOTAL OUTBOUND MOVEMENTS
Movement
Right -Out At FFB White Chapel Drive
Right -Out At Common White Chapel Drive
Left -Out At Common White Chapel Drive
Right -Out At FM1709 Driveway
TOTAL SITE OUTBOUND
TOTAL TRIPS
Allocation
Fraction
Daily
AM Peak
PM Peak
Sat. Peak
0.241
583
67
46
69
0.143
347
34
26
39
0.200
484
52
37
58
0.416
1008
105
76
116
2422
258
185
282
Allocation
Fraction
Daily
AM Peak
PM Peak
Sat. Peak
0.1
230
16
24
24
0.100
230
16
24
24
0.300
689
47
73
72
0.500
1148
79
121
120
2297
157
242
241
Allocation
Fraction
Daily
AM Peak
PM Peak
Sat. Peak
0.200
25
4
5
4
0.000
0
0
0
0
0.300
38
6
8
6
0.500
63
10
13
10
125
20
25
20
Allocation
Fraction
Daily
AM Peak
PM Peak
Sat. Peak
0.105
255
20
29
28
0.095
230
16
24
24
0.300
726
53
80
78
0.500
1211
89
134
130
2422
177
267
261
4843
435
452
543
TABLE 4 - INTERSECTION MOVEMENTS - FM 1709 AND WHITE
Intersection Movement
NBL
NBT
NBR
EBL
EBT
EBR
SBL
SBT
SBR
WBL
W BT
WBR
Intersection Movement
NBL
NBT
NBR
EBL
EBT
EBR
SBL
SBT
SBR
WBL
W BT
WBR
Intersection Movement
NBL
NBT
NBR
EBL
EBT
EBR
SBL
SBT
SBR
WBL
W BT
WBR
CHAPEL BLVD.
WEEKDAY TOTALS
In
Out
0.0
363.2
0.0
363.2
0.0
0.0
0.0
363.2
0.0
847.6
0.0
0.0
0.0
0.0
363.2
0.0
0.0
0.0
566.2
0.0
281.3
0.0
0.0
0.0
TOTAL MOVEMENTS
26.9
AM PEAK HOUR
In
Out
0.0
% of New Intersection
Total
In %
Out %
Traffic
363.2
0.0
15.0
11.5
363.2
0.0
15.0
11.5
0.0
0.0
0.0
0.0
363.2
0.0
15.0
11.5
847.6
0.0
35.0
26.9
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
363.2
15.0
0.0
11.5
0.0
0.0
0.0
0.0
566.2
23.4
0.0
18.0
281.3
11.6
0.0
8.9
0.0
0.0
0.0
0.0
3,148.2
20.8
11.3
0.0
AM PEAK HOUR
In
Out
0.0
26.6
0.0
26.6
0.0
0.0
0.0
26.6
0.0
62.1
0.0
0.0
0.0
0.0
38.7
0.0
0.0
0.0
62.3
0.0
27.9
0.0
0.0
0.0
TOTAL MOVEMENTS
In
Out
Total
% of New Intersection
Total
In %
Out %
Traffic
26.6
0.0
15.0
9.8
26.6
0.0
15.0
9.8
0.0
0.0
0.0
0.0
26.6
0.0
15.0
9.8
62.1
0.0
35.0
22.9
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
38.7
15.0
0.0
14.3
0.0
0.0
0.0
0.0
62.3
24.2
0.0
23.0
27.9
10.8
0.0
10.3
0.0
0.0
0.0
0.0
270.7
20.8
11.3
0.0
In
Out
Total
In %
Out %
0.0
40.1
40.1
0.0
15.0
0.0
40.1
40.1
0.0
15.0
0.0
0.0
0.0
0.0
0.0
0.0
40.1
40.1
0.0
15.0
0.0
93.6
93.6
0.0
35.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
27.7
0.0
27.7
15.0
0.0
0.0
0.0
0.0
0.0
0.0
43.9
0.0
43.9
23.7
0.0
20.8
0.0
20.8
11.3
0.0
0.0
0.0
0.0
0.0
0.0
TOTAL MOVEMENTS
306.3
% of New Intersection
Traffic
13.1
13.1
0.0
13.1
30.5
0.0
0.0
9.1
0.0
14.3
6.8
0.0
Traffic Study Page 14
Southlake Commons in Southlake, Texas February 19, 2017
VIII. Access Spacing Along FM 1709 and White Chapel
The proposed Southlake Commons and existing First Financial Bank are expected to
share the single existing driveway onto FM 1709 (Driveway A). The centerline of this
existing driveway is located approximately 505' west of the west curb line of White
Chapel Blvd, and its most easterly curb return is located approximately 35' west of
the beginning of the transition for the dedicated eastbound right turn lane on FM
1709 as it approaches White Chapel Blvd. The nearest existing driveway on the
south side of FM 1709 is located approximately 515' (centerline to centerline) west of
the existing driveway serving First Financial Bank and Southlake Commons.
City of Southlake driveway separation requirements along FM 1709 require a
minimum centerline driveway spacing of 500'. TXDOT access management
requirements specify a minimum edge to edge driveway spacing of 360' at a speed
limit of 45 mph. The existing driveway location appears to meet both requirements.
IX. Deceleration Lane Requirements
The driveway onto FM1709 is served by an existing deceleration lane. Compliance
of this driveway and deceleration lane with current TXDOT and city standards has
not been investigated in preparing this report, however, BDI designed these
improvements in 2010 and is not aware of any deficiencies related to them. In the
event that the developer wishes to construct a median opening adjacent to the drive
approach onto FM 1709, it should be noted that a median opening in this location
would not comply with TXDOT standards and the likelihood of obtaining a median
opening in this location is very low.
The City of Southlake Driveway Ordinance No. 634 requires a deceleration lane for
speeds limits greater than 40 mph with more than 40 right turning movements per
hour, or for any driveway projected to have 50 or more right -turn ingress movements
per hour. For the First Financial Bank driveway onto White Chapel Blvd. (Driveway
B), this threshold is shown to be exceeded during both the AM peak and Saturday
peak hours (with 70 and 75 right turns per hour, respectively).
Due to a variety of grading challenges, utility clearance issues, and lack of adequate
horizontal spacing, and due to the fact that there are two existing southbound lanes
in White Chapel Blvd. in this area, with the right lane potentially functioning as a
deceleration and turning lane and the left lane acting as a through -lane, city staff
have expressed willingness to consider a variance from the conditions of Ordinance
No. 634. In pursuing this variance, BDI believes that concerns regarding restriping
and replacement/addition of signage will need to be addressed.
Traffic Study Page 15
Southlake Commons in Southlake, Texas February 19, 2017
X. Sight Distances Along FM 1709 and White Chapel
A detailed survey of FM 1709 and White Chapel to establish sight distances has not
been conducted as a part of this study. However, from recent field visits and
photographs taken of the site, the sight distance from the FM 1709 driveway
(Driveway A) to the west appears to be in excess of 1,000 feet. The sight distance to
the east appears to be in excess of 700 feet.
At the Common White Chapel Blvd. driveway (Driveway C), the sight distance to the
north is approximately 700 feet, while the sight distance to the south is approximately
432 feet, as measured in a piecewise-li near fashion from aerial photographs along
the northbound left lane (Ref. Exhibit 1). Due to curvature in the horizontal alignment
of the roadway, the sight line to the north extends over roadway shoulder and private
property, and future growth of vegetation or placement of obstacles in this area could
reduce future sight distance (Ref. Exhibit 2). A similar situation exists to the south,
where future growth of vegetation combined with a failure to trim undergrowth would
also reduce sight distance (Ref. Exhibit 3). Recommended maintenance practices to
preserve sight distances are provided in Section XI. Curvature in the vertical
alignment of White Chapel Blvd. reduces the visibility to the north somewhat,
resulting in a visibility "local minimum" condition at the intersection of the south curb
of FM 1709 and the west curb of White Chapel Blvd. However, it appears that even
this location meets the visibility requirements for AASHTO's intersection sight
distance, such that a 3.5' object is visible from 3.5' above grade at the common
driveway onto White Chapel Blvd. Visibility improves both to the north and south of
this location.
AASHTO's intersection sight distance d = 1.47*V*tg, where d is the sight distance in
feet, V is the posted speed limit in MPH, and tg is the time gap, or time required for a
vehicle to accelerate into a lane of traffic. 7.5 seconds is considered a typical base
value for a passenger vehicle time gap, and this value is normally increased by 0.5
seconds for each lane the vehicle must cross while maneuvering. For the left turning
movement at the Common White Chapel driveway (Driveway C), a vehicle must
cross two lanes of traffic and a median approximately two lanes in width, so a time
gap of 9.0 seconds is used here. Thus the minimum intersection sight distance is
396.9 feet. For the case of single -unit trucks, the time gap is increased by an
additional two seconds, resulting in a minimum intersection sight distance of 485.1
feet, which exceeds the existing sight distance. Therefore, this intersection does not
comply with AASHTO design criteria for truck traffic. [The Civil Engineering
Handbook, 2nd ed., CRC Press, Chen and Liew, eds., 2003. Chapter 63, Geometric
Design.]
Traffic Study Page 16
Southlake Commons in Southlake, Texas February 19, 2017
XI. Recommendations to Improve Future Traffic Conditions
BDI recommends the following improvements to the site to improve the flow of traffic
in the future:
• Consider placing a stop sign and stop bars at the existing driveway exit onto
White Chapel.
• Prevent new planting of trees and shrubs, as well as placement of other new
obstacles at ground level, north of the Common Driveway onto White Chapel
(Driveway C). Maintain existing tree trimming practices to remove new
branch growth below bottom level of existing tree canopies.
• Trim trees and shrubs to prevent growth above the sidewalk south of the
Common Driveway onto White Chapel (Driveway C) below a height of
approximately eight feet above grade.
Traffic Study
Southlake Commons in Southlake, Texas
XII. Summary
Page 17
February 19, 2017
Conifer Real Estate commissioned BDI to provide this Traffic Study in order to obtain
site plan and other necessary permit approvals for development of Southlake
Commons.
BDI estimated trips generated based on anticipated uses provided by the developer
in accordance with the Institute of Transportation Engineers' Trip Generation Manual,
9t" Edition and distributed these trips along the adjacent roadways in a
demographically appropriate manner. 2015 traffic volumes for FM 1709 published by
the City of Southlake were provided for comparison with Southlake Commons trip
generation calculations.
Because calculated right -in turn volumes exceed those allowed by the City of
Southlake without a right -turn deceleration lane, it has been recommend that the
client pursue a variance from Ordinance No. 634. The city may require alterations to
street striping and signage, as well as other remedial measures it determines to be
necessary, in exchange for granting a variance.
Digitally signed by Noah
Noah Boydston
DN: cn=Noah Boydston,
o=Boydston Designs Inc.,
Bod s t o n em Vice President,
y email=ncb@bdi-eng.com, c=US
Date: 2017.02.19 18:42:54 -06'00'
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