HomeMy WebLinkAboutSD-23-10 - Supplemental - 0255 Kennedy Drive (7)
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TECHNICAL MEMORANDUM
Project: O’Brien Home Farm - Hillside PUD Lots 10 & 11
Date: August 30, 2021
From: Roger Dickinson, PE, PTOE
Subject: Updated Traffic Impact Assessment
Introduction
This technical memorandum updates the original Traffic Impact Assessment (TIA)1 for Phase 1 of the
proposed O’Brien Home Farm planned unit development, now known as “Hillside” (the Project). This
update specifically examines the following items:
C The Project’s estimated trip generation based on changes made since the original TIA together
with the proposed development on Lots 10 & 11.
C Future traffic congestion conditions at the new Kennedy Dr/Two Brothers Dr intersection
C An assessment of the warrants for signalization to identify when the proposed traffic signal should
be installed at the new Kennedy Dr/Two Brothers Dr intersection.
C The Project’s estimated City and Act 145 transportation impact fees.
Construction of the Project has been underway for several years now, generally proceeding in the
easterly direction from Hinesburg Rd along O’Brien Farm Rd2 and Two Brothers Drive on Lots 5-9.
Approximately 75 of the 115 approved single and duplex residential units have sold to date, with the
remainder anticipated to be sold by the end of 2022. Access to the constructed units is presently
to/from Hinesburg Rd via O’Brien Farm Rd and to/from Kennedy Dr via Eldredge St.
The next lots proposed for development are Lots 10 & 11. Two multi-family buildings housing 47 units
each, for a total of 94 additional residential units on these two lots. The development of Lots 10 & 11
also includes extending Two Brothers Dr and constructing its new intersection with Kennedy Dr; opening
a third access route to the Project.
The entire Hillside planned unit development will ultimately include a total of 115 single and duplex
residential units on Lots 5-9, and 416 multi-family residential units (apartments) plus 3,500 sf of general
office space on Lots 10-15.3
1 O’Brien Home Farm PUD - Phase 1, Traffic Impact Assessment, Lamoureux & Dickinson, August 8, 2016
2 O’Brien Farm Rd now includes the westerly segment of what was formerly Eldredge St between Hinesburg Rd
and Two Brothers Dr.
3 Please note that the 416 apartments includes a proposed bonus density for the excess inclusionary units
provided. While this bonus density is not yet confirmed, it is requested in the current application.
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Project-Generated Trips
The additional new trip generation of this Project was estimated using trip generation data published by
the Institute of Transportation Engineers (ITE)3, 4 for the proposed land-use categories. With this Project
being constructed in discrete construction phases, the trip generation has been estimated for each
phase.
Table 1 shows the estimated peak hour vehicular trip generation from the original TIA. Table 2 shows
the updated estimated peak hour vehicular trip generation, incorporating the project revisions made
since the original TIA. Table 2 also updates the estimated peak hour vehicular trip generation using the
current edition of Trip Generation.
Table 1 - Project Trip Generation (Original TIA)4
(vehicle trip ends per hour)
Phase Proposed Land-Use
ITE
Land-Use
Category
AM Peak Hour PM Peak Hour
Enter Exit Total Enter Exit Total
Lots
5-9
59 single family residential units
58 duplex (condominium) units
Subtotal
210
230
11
7
18
33
31
64
44
38
82
44
29
73
26
14
40
70
43
113
Lots
10-15
300 apartment units
55,000 sf commercial/office
Subtotal
220
varies
30
112
142
121
22
143
151
134
285
119
32
151
64
100
164
183
132
315
Total 160 207 367 224 204 428
Table 2- Project Trip Generation (Updated)5
(vehicle trip ends per hour)
Phase Proposed Land-Use
ITE
Land-Use
Category
AM Peak Hour PM Peak Hour
Enter Exit Total Enter Exit Total
Lots
5-9
71 single family residential units
44 duplex (low-rise multi-family) units
Subtotal
210
220
13
5
18
40
17
57
53
22
75
46
18
64
27
10
37
73
28
101
Lots
10-15
416 mid-rise multi-family units
3,500 sf general office
Subtotal
221
710
36
3
39
102
1
103
138
4
142
106
1
107
68
4
72
174
5
179
Total 57 160 217 171 109 280
4 Trip Generation, Institute of Transportation Engineers, 9th Edition
5 Trip Generation, Institute of Transportation Engineers, 10th Edition
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The peak hour trips for Lots 10 and 11 are included in peak hour trips for the 416 mid-rise multi-family
residential units shown in Table 2 above. Because the ITE peak hour trip generation equations in the
residential land-use categories are not linear, the peak hour trips for only Lots 10 and 11 are best
calculated by pro-rating the above trips based on the number of mid-rise multi-family units. Table 3, on
the following page, shows the estimated peak hour trips for Lots 10 and 11.
Table 3- Lots 10 & 11 Peak Hour Trip Generation
(vehicle trip ends per hour)
Phase Proposed Land-Use
AM Peak Hour PM Peak Hour
Enter Exit Total Enter Exit Total
Lots 10 & 11 94 mid-rise multi-family units 8 23 31 24 15 39
Using the same project trip directional patterns which were used in the original TIA results in the peak
hour project-generated turning movements at the Kennedy Dr/Two Brothers Dr intersection shown in
Figure 1. Detailed trip generation and directional distribution calculations are enclosed in Appendix A.
Note: Appendices are included under separate cover.
Figure 1 - New Hillside-Generated Peak Hour Trips
AM Peak Hour PM Peak Hour
Kennedy
Dr
3 0 Kennedy
Dr
Kennedy
Dr
2 0 Kennedy
Dr261473 43
78 37 N 54 25 N
Two Brothers Dr Two Brothers Dr
No-Build Traffic Volumes
The original TIA for this Project anticipated that it would be constructed during the 2017-2020 time
period, and incorporated the standard five-year projection from completion of construction, to year
2025, in order to examine potential traffic impacts. This update anticipates that construction will now
be completed by 2025, and projects future no-build traffic volumes out to the year 2030.
Peak hour intersection turning movement volumes were obtained from more recent traffic counts
performed on Kennedy Dr by the Vermont Agency of Transportation (VTrans). These include a turning
movement (TM) count at the Kennedy Dr/Hinesburg Rd intersection on July 2-3, 2018 and an automatic
traffic recorder (ATR) count at Station D223 (located between Hinesburg Rd and Kimball Ave) during the
week of July 13-19, 2018.
Hourly traffic data from continuous count station (CTC) D099, located on I-189 in South Burlington, was
examined to calculate a design hour volume (DHV) adjustment factor for the pm peak hour on July 2,
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2018. Normally, the DHV adjustment factor would be applied to the peak hour volumes observed
during the TM count at the Kennedy Dr/Hinesburg Rd intersection. The resulting adjustment factor
equaled 1.043, and would have increased the pm peak hour traffic volume on Kennedy Dr east of
Hinesburg Rd to only 1,243 vehicles per hour (vph). In comparison, the observed maximum peak hour
observed in the 2018 ATR count at Station D223 was 1,492 vph (Wednesday, 5-6 pm). This latter
volume slightly exceeds the projected 2025 No-Build DHV in the original TIA for this Project, and appears
to be a more accurate estimate of the 2018 DHV.
The observed peak hour volumes were further adjusted to account for background traffic growth using
historical traffic growth rates and projections obtained from VTrans.6 From that, a 3.7% background
growth rate was also applied to adjust from years 2018 to 2030. Detailed DHV calculations are enclosed
in Appendix B.
Figures 2 and 3, below, respectively present the resulting estimated 2030 No-Build and Build peak hour
turning movement volumes at the new Kennedy Dr/Two Brothers Dr intersection. With Hillside’s
reduced peak hour trip generation, future turning movements entering and exiting the Two Brothers
Drive are similarly reduced.
Figure 2 - 2030 No-Build Peak Hour Volumes
AM Peak Hour PM Peak Hour
Kennedy
Dr
772 587 Kennedy
Dr
Kennedy
Dr
698 849 Kennedy
Dr000 0
0 0 N 0 0 N
Two Brothers Dr Two Brothers Dr
Figure 3 - 2030 Build Peak Hour Volumes
AM Peak Hour PM Peak Hour
Kennedy
Dr
775 587 Kennedy
Dr
Kennedy
Dr
700 849 Kennedy
Dr26 1473 43
78 37 N 54 25 N
Two Brothers Dr Two Brothers Dr
Traffic Congestion
Traffic congestion conditions are identified by “levels of service”, commonly referred to as “LOS”. The
ranges are A to F; where A represents essentially free flow (no congestion), C represents average
congestion, and F represents severe congestion. At signalized intersections, the LOS is determined by
6 Continuous Traffic Counter Report Based on 2020 Traffic Data, Vermont Agency of Transportation, May 2021
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the overall delay experienced by all turning and through movements. At unsignalized intersections, the
LOS is determined by the minor-street approach having the lowest LOS. The level of service criteria for
intersections is shown in Table 4.
Table 4 - Level of Service/Delay Criteria7
LOS
Average Delay (sec/veh)
LOS
Average Delay (sec/veh)
Signalized Unsignalized Signalized Unsignalized
A
B
C
≤10
≤20
≤35
≤10
≤15
≤25
D
E
F
≤55
≤80
>80
≤35
≤50
>50
In Vermont, LOS C represents the desired design standard for roadways and signalized intersections.8
At two-way stop controlled (unsignalized) intersections having greater than 100 vph approach volume
on a single-lane side street approach or greater than 150 vph approach volume on a two-lane side street
approach, the VTrans level of service policy establishes LOS D as the desired design standard on the
minor street approach(s). There is no level of service standard for unsignalized intersections not
meeting the above side street volume thresholds. Reduced levels of service are acceptable in densely
settled areas where volume/capacity ratios remain below 1.0 and/or the improvements required to
achieve LOS C would create adverse environmental and cultural impacts.
In addition, Section 15.12.F of the City of South Burlington’s Land Development Regulations require that
signalized intersections in the vicinity of a development have an overall level of service D or better, with
through movements on the major roadways also experiencing level of service D or better at full build-
out.
Two Brothers Dr will be extended to Kennedy Dr and the new Kennedy Dr/Two Brothers Dr intersection
will be constructed concurrently with the development of Lots 10 and 11. The intersection’s initial
construction includes installing exclusive left- and right-turn lanes exiting Two Brothers Dr and an
exclusive left-turn lane on Kennedy Dr to separate left-turning traffic entering this Project from
westbound through traffic. This new intersection will also initially operate as an unsignalized
intersection using two-way stop control until such time as the traffic volumes exiting Two Brothers Dr
satisfy one or more of the MUTCD9 warrants for signalization. Ultimately, however, it is anticipated that
the proposed future development of the O’Brien Home Farm will warrant the installation of a traffic
signal. Plans showing this new intersection (including for a traffic signal) are submitted under separate
cover.
It is noted that with two approach lanes exiting Two Brothers Dr, future Hillside peak hour volumes
exiting Two Brothers Dr will be less than the 150 vph minor street approach volume threshold in VTrans’
level of service policy. Intersection capacity analyses were nonetheless performed to determine future
levels of service during year 2030 “Build” scenarios under both unsignalized and signalized control.
7 Highway Capacity Manual, Transportation Research Board, 6th Edition
8 Highway Design “Level of Service” Policy, Vermont Agency of Transportation, May 31, 2007
9 Manual on Uniform Traffic Control Devices, Federal Highway Administration, 2009
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Table 5 presents the results of those analyses. Detailed capacity analysis results are enclosed in
Appendix C.
Table 5 - Kennedy Dr/Two Brothers Dr
Intersection Capacity Analyses Results - 2030 Build
Approach / Lane Group
AM Peak Hour PM Peak Hour
LOS Delay V/C Max Q LOS Delay V/C Max Q
Unsignalized
Two Brothers Dr NB LT
Two Brothers Dr NB RT
Kennedy Dr WB LT
E
B
A
35.6
11.5
9.6
0.40
0.06
0.02
48’
5'
3'
E
B
A
41.6
11.2
9.6
0.36
0.04
0.05
40'
3'
5'
Signalized
Kennedy Dr EB TH/RT
Kennedy Dr WB LT
Kennedy Dr WB TH
Two Brothers Dr NB LT
Two Brothers Dr NB RT
OVERALL
A
D
A
D
C
A
4.6
42.9
1.8
42.2
35.5
6.6
0.31
0.19
0.21
0.52
0.19
185'
28'
71’
90'
25'
A
D
A
D
C
A
5.1
42.3
2.0
41.1
33.6
6.0
0.31
0.37
0.29
0.39
0.11
180'
59’
100’
69'
20'
The results of the intersection capacity analyses show that vehicles exiting Two Brothers Dr will initially
experience long delays during peak periods under two-way stop-control as Hillside development
progresses. Ultimately, however, future traffic congestion conditions on Two Brothers Dr will improve
to LOS D once the proposed traffic signal is installed. Kennedy Dr through traffic levels of service will
remain at LOS A.
Signal Warrant Examination
Full operation of the new traffic signal at the Kennedy Dr/Two Brothers Dr intersection should not
commence until future traffic volumes exiting Two Brothers Dr satisfy either the MUTCD’s four-hour or
peak hour volume warrants. This will be driven primarily by left-turn movement volumes exiting Two
Brothers Dr (see below), and will require periodic traffic monitoring as construction of Hillside Lots 10-15
phase and O’Brien Brothers’ proposed Eastview development advance.
There are several volume-related warrants for signalization, each having different time periods; 8 hours,
4 hour and 1 hour. This examination will examine only the latter two; Warrants #2 - Four-Hour Volume
and #3 - Peak-Hour Volume. These two warrants are examined graphically using curves from the
MUTCD; which are shown in Figures 4C-2 and 4C-4 on the following pages. These curves require two
volumes; the first being the total two-way volume of traffic approaching the intersection on the major
street (Kennedy Dr) and the volume of traffic approaching the intersection on the higher-volume minor
street. At this intersection, Two Brothers Dr is the only minor street and its approach volumes would be
the turning movements exiting onto Kennedy Dr.
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The volumes shown in Table 6 were used to examine the four-hour and peak-hour warrants. The
Kennedy Drive volumes shown in Table 6 were obtained from the 2018 automatic traffic count at
Station D223 (adjusted to the year 2025). Two Brothers Drive volumes were estimated using ITE hourly
trip generation data for residential land-uses.
Table 6 - Kennedy Dr/Two Brothers Dr
2025 Weekday Volumes & Signal Warrant Examination
Hour
Kennedy Dr
Two-Way
Volumes*
Two Brothers Dr
Approach Volumes*
Signal Warrants
Satisfied? (Y/N)
LT Exit RT Exit Total
Warrant 2
Four Hour
Warrant 3
Peak Hour
8-9 am 1,242 79 37 116 Y Y
9-10 am 1,069 53 25 78 N** N
10-11 am 1,068 41 19 60 N N
11-12 pm 1,173 41 19 60 N N
12-1 pm 1,282 36 17 53 N N
1-2 pm 1,209 35 16 51 N N
2-3 pm 1,122 41 19 60 N N
3-4 pm 1,225 44 21 65 N N
4-5 pm 1,352 48 23 71 N N
5-6 pm 1,395 53 25 78 N** N
* vehicles per hour ** close to satisfying
As can be seen in Figures 4C-2 and 4C-4 on the following page, the Kennedy Dr peak period volumes are
such that the minimum minor-street approach thresholds (on the far right of the graphs) apply during
those periods. The applicable curve for this intersection in each graph is the upper “2 OR MORE LANES
& 2 OR MORE LANES” curve.
The updated weekday peak hour traffic projections indicate that the projected morning peak hour
volumes will satisfy Warrant 3 - Peak Hour Volume. Warrant 3 was also checked for a partial-build
scenario wherein 345 out of the 416 proposed mid-rise multi-family units (apartments) are
constructed.10 That analysis estimated the morning peak hour volume exiting Two Brothers Dr to be 103
vph; just crossing the 100 vph threshold to satisfy Warrant 3 during the morning peak hour.
Warrant 2 - Four Hour Volume is also met during the morning peak hour, but requires four hours to be
satisfied. As can be seen in Table 6, though, there are two additional hours which will be close to
meeting this warrant as Hillside development approaches completion. It can be reasonably expected
that O’Brien Home Farm’s future Eastview development, located adjacent to and interconnected with
Hillside, will cause Warrant 2 to be fully satisfied.
10 Including 251 apartments in the next Hillside development phase following Lots 10-11.
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Multi-Modal Facilities
Two Brothers Dr will include a new 10 ft wide shared use path on its west side and a 5 ft wide sidewalk
on its east side. These facilities will link the existing sidewalk on the south side of Kennedy Dr with other
internal Project sidewalks and paths. The existing shared use path on the north side of Kennedy Dr will
also be accessed by installing a new marked crosswalk crossing Kennedy Dr at the Kennedy Dr/Two
Brothers Dr intersection.
With Kennedy Dr being a wide four-lane highway having moderate (40-45 mph) vehicle speeds and high
traffic volumes, pedestrians will likely find it difficult to safely cross Kennedy Dr during peak periods at
the Two Brothers Dr intersection. It is proposed, therefore, that the initial construction of this
intersection include the installation of a rectangular rapid flashing beacon (RRFB) until such time as the
traffic signal is warranted and installed.
The above pedestrian and bicycle facilities on Two Brothers Dr will also enable ready access to existing
nearby Kennedy Dr bus stops.
Transportation Impact Fees
The City of South Burlington’s Impact Fee Ordinance assesses a road improvement impact fee on new
development to help fund designated highway and intersection improvements throughout South
Burlington (as identified in the City’s Impact Fee Ordinance). For single family dwellings and multi-family
dwellings, the base fees equal $1,010 per unit and $670 per unit, respectively. For non-residential
development, the base fee equals $1,000 per pm peak hour vehicle trip end. Using Hillside’s proposed
development in each of those categories, the City’s base road improvement impact fee is estimated to
equal $379,910.
The City of South Burlington also assesses a recreation impact fee on new residential development; a
large majority of which is to help fund the construction of designated sidewalks, recreation paths,
bicycle lanes and other pedestrian improvement projects throughout South Burlington. For structures
containing three or fewer residential units, the base fee equals $1,686 per unit. For structures
containing four or more units, the base fee equals $1,180 per unit. Using Hillside’s proposed
development in each of those categories, the City’s base recreation impact fee is estimated to equal
$684,770.
VTrans also assesses a statewide transportation impact fee (Act 145 Impact Fee) on new development
projects. The amount of this impact fee was initially presented in a letter from this office dated May 26,
2017 to Christopher Clow, PE, of VTrans. Those calculations were updated using the same methodology
that was used in the foregoing letter, but with the reduced pm peak hour trip generation outlined in
Table 2. The results are presented in Table 7. Detailed calculations are enclosed in Appendix D.
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Table 7 - Act 145 Transportation Impact Fee Summary
Highway Improvement Project
PM Peak
Hour Trips
Impact
Fee/Trip
Capital Project
Impact Fee
Champlain Parkway 4 $2,069 $8,276
Burlington Roundabout 8 $1,217 $9,736
VT 2A & James Brown Dr 6 $189 $1,134
VT 2A & Industrial Ave/Mountain View Rd 11 $252 $2,772
US 2 & Trader Lane 6 $210 $1,260
I-89 Exit 12 8 $243 $1,994
Subtotal $25,122
15% Travel Demand Management Credit -
extensive sidewalks, bike paths, new Hinesburg Rd crosswalk with RRFB,
new Kennedy Dr crosswalk with RRFB or pedestrian signals
-$3,768
Total Act 145 Impact Fee $21,354
The above Act 145 Impact Fee represents a reduction from the $27,749 total fee which is referenced in
Hillside’s Act 250 permit.11 Inasmuch as a portion of that fee has already been paid, Table 8 presents the
remaining amount to be paid.
Table 8 - Adjusted Act 145 Transportation Impact Fee
Development Phase # Units PM Peak Hour Trips Act 145 Impact Fee
Proposed Full Build 531 280 $21,354
The updated Act 145 Impact Fee equals $76.26 per pm peak hour trip end.
Lots 5-9
Updated Impact Fee
Paid To Date
Balance
115
113
$8,617
$7,325
$1,292
Lots 10-11 94 39 $2,974
Future Phases (Lots 12-15) 322 128 $9,763
Conclusions & Recommendations
From the foregoing analyses, we conclude that acceptable future traffic congestion conditions will be
maintained with the development of Lots 10-11 and the proposed remaining units of this Project. In
addition, we recommend that a Rectangular Rapid Flashing Beacon (RRFB) be installed at the new
Kennedy Dr/Two Brothers Dr intersection as part of the initial construction of that intersection, until
such time as the traffic signal and its pedestrian signals are warranted and installed.
11 Land-Use Permit 4C1106-3, Findings of Fact #81-83