HomeMy WebLinkAbout18 - Traffic Impact Study - W Babcock_Fowler Intersection
July 24, 2018
Mr. Shawn Kohtz
Interim Director of Public Works
City of Bozeman
20 East Olive Street
Bozeman, MT 59715
Reference: Revised West Babcock Street & Fowler Avenue Traffic Analysis
17097.04
Dear Shawn:
The purpose of this letter is to summarize the findings of the revised traffic analysis we recently
completed at the intersection of West Babcock Street and Fowler Avenue in Bozeman. As you
know, this intersection had previously been identified as having a level-of-service deficiency. A
traffic letter addressed to Craig Woolard on March 2, 2018 summarized the traffic analysis of the
intersection with three potential new developments (McIntosh, Hanser, and Nelson) in the area.
The March letter showed that the West Babcock Street and Fowler Avenue intersection could
accommodate the new site-generated traffic along with a 2% background growth rate for five years
at an acceptable Level of Service (LOS) with the existing geometrics and one-way stop control. This
analysis included the provision for a two-stage northbound left-turn using the existing two-way left-
turn lane on Babcock Street.
Since the last letter submittal, the McIntosh Development’s proposed plan has changed to a denser
land use. The development plans now include a 3-story building with 60 two-bedroom apartments,
compared to the original assumption of 18 single-family homes. The attached vicinity map shows
the location of the three proposed developments relative to the subject intersection. The proposed
developments, with the McIntosh updates, include the following:
· McIntosh Development – Tract 24 – Proposed 60 two-bedroom apartments
· Hanser Development – Lots 3 and 4, Parkway Plaza Subdivision – Proposed two 12,000
square-foot medical-dental office buildings
· Nelson Development – Lots 1 and 2, Parkway Plaza Subdivision – Proposed two 12,000
square-foot general office buildings
The traffic volumes collected in January 2018 were again used for this analysis and were adjusted for
seasonal variation using MDT’s seasonal adjustment factors. These volumes were then compared to
those from previous studies conducted in 2015 and 2016, as shown in the attached Volume
Summary figure. This comparison shows that the total entering volume at this intersection decreased
by 10% from 2015 to 2016 and then again by another 4% from 2016 to 2018. The decreasing
volume at this intersection is presumably due to a shift in traffic patterns caused by nearby network
improvements that the City has recently made.
Mr. Shawn Kohtz
July 24, 2018
Page 2
The attached Trip Generation Summary shows the number of trips projected for each development
based on the average rates provided in the ITE Trip Generation manual, 10th Edition. This table has
been updated to reflect the changes to the proposed McIntosh development. These trips were again
assigned to the existing roadway network based on the distribution of existing traffic volumes at the
intersections of Babcock Street/Fowler Avenue and Laramie Drive/Fowler Avenue. The assigned
traffic volumes were then added to the existing 2018 volumes and the resulting Existing + Site
volumes are shown in the attached volume figure for reference.
The final attachment to this letter presents a summary of the capacity analysis completed for this
project. The analysis was completed for Existing and Existing + Site volumes, and results are shown
with and without consideration for the potential to use the existing two-way left-turn lane on
Babcock Street as storage for a two-stage northbound left turn. With this provision accounted for,
the northbound approach would operate at LOS C for Existing + Site volumes and would drop to
LOS D without it. The final set of capacity analysis results show that the intersection could
accommodate a growth rate of an additional 2% per year for the next 5 years and the northbound
approach would still operate at LOS C (including the provision for the two-stage turn using the two-
way left-turn lane). Given that volumes at this intersection have decreased over the last several years,
this should be adequate reserve capacity until the City’s future Fowler Avenue improvements are
constructed. These results are all consistent with the findings of the March 2018 traffic letter, even
with the proposed increase in units.
As noted in the March 2018 letter, the feedback from a February 15, 2018 meeting noted the
options for a waiver to be granted for any improvements at this intersection for all three of the
proposed developments noted above, as long as their site plan applications are approved within two
years of this analysis. If the developments do not move forward within that timeframe, traffic
volumes at this intersection will need to be evaluated again. Finally, it is our understanding that this
letter and corresponding analysis will fulfill the traffic impact study requirement for all three of the
proposed developments. Please confirm these items still stand with this updated traffic analysis at
your convenience.
Please feel free to contact me at 406/922-4306 or jstaszcuk@sandersonstewart.com if you have any
questions or need further information.
Sincerely,
Joey Staszcuk, PE, PTOE
Project Transportation Engineer
JHS/drs
Enc.
V:17097_04_Kohtz_Letter_072418_SC
9,0280.3
Miles
This product is for informational purposes and may not have been prepared for, or be suitable for legal,
engineering, or surveying purposes. Users of this information should review or consult the primary data and
information sources to ascertain the usability of the information. Feet
1,0510
Legend
526
Location
1,051
D. Scharf
03/01/2018
Created By:
Created For:
Date:
Babcock & Fowler Traffic Analysis
Street Names
City Limits
Intensity Units total enter exit total enter exit
Multifamily Housing (Mid-Rise) (Land Use Code 221)1 60 Dwelling Units 22 6 16 26 16 10
22 6 16 26 16 10
Medical-Dental Office Building (Land Use Code 720)2 24 1000 ft2 GLA 67 52 15 83 23 60
67 52 15 83 23 60
General Office Building (Land Use Code 710)3 24 1000 ft2 GLA 28 24 4 28 4 24
28 24 4 28 4 24
117 82 35 137 43 94
(1) Multi-Family Housing (Mid-Rise) - Land Use Code 221 Units = Dwelling Units
Peak Hour of the Adjacent Street, One Hour between 7 and 9 AM: Average Rate = 0.36 (26% entering, 74% exiting)
Peak Hour of the Adjacent Street, One Hour between 4 and 6 PM: Average Rate = 0.44 (61% entering, 39% exiting)
(2) Medical-Dental Office Building - Land Use Code 720 Units = 1000 SF GLA
Peak Hour of the Adjacent Street, One Hour between 7 and 9 AM: Average Rate = 2.78 (78% entering, 22% exiting)
Peak Hour of the Adjacent Street, One Hour between 4 and 6 PM: Average Rate = 3.46 (28% entering, 72% exiting)
(3) General Office Building - Land Use Code 710 Units = 1000 SF GLA
Peak Hour of the Adjacent Street, One Hour between 7 and 9 AM: Average Rate = 1.16 (86% entering, 14% exiting)
Peak Hour of the Adjacent Street, One Hour between 4 and 6 PM: Average Rate = 1.15 (16% entering, 84% exiting)
*Trip Generation, 10th Edition, Institute of Transportation Engineers, 2017
Trip Generation Summary
Land Use
Independent Variable AM Peak Hour PM Peak Hour
McIntosh Development
Total New External Personal Vehicle
Hanser Development
Total New External Personal Vehicle
Nelson Development
Total New External Personal Vehicle
TOTALS FOR ALL DEVELOPMENTS
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NB 27.9 D 6 Avg Delay (s/veh) LOS95th % Queue (veh)Avg Delay (s/veh) LOS95th % Queue (veh)EB -- -- --WB 1.6 A 1 NB 24.2 C 5Intersection Control One-Way (NB) Stop Control West Babcock Street &South Fowler AvenueIntersection ApproachFuture (2023) @ 2% AGR + Site AM Peak PM PeakIntersection Control One-Way (NB) Stop Control West Babcock Street &South Fowler AvenueIntersection Control One-Way (NB) Stop Control West Babcock Street &South Fowler Avenue Intersection ApproachFuture (2023) @ 3% AGR + Site AM Peak PM PeakIntersection ApproachFuture (2023) @ 4% AGR + Site AM Peak PM Peak
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