HomeMy WebLinkAboutRS_GMC Addition-Trip Gen Assessment_220127_v1.pdf215 SW 12TH STREET
TRIP GENERATION ASSESSMENT
Renton, WA
Prepared for: Mr. Brad Brotherton
Brotherton Cadillac/GMC/Buick
215 SW 12th Street
Renton, WA 98055
January, 2022
HEATH & ASSOCIATES, INC Transportation and Civil Engineering
PO Box 397 Puyallup, WA 98371 (253) 770 1401 heathtraffic.com
01/27/2022
January 27, 2022
Mr. Brad Brotherton
Brotherton Cadillac/GMC/Buick
215 SW 12th Street
Renton, WA 98055
The intent of this assessment is to provide the city of Renton with a trip generation summary and
site characteristics for the proposed project herein referred to as 215 SW 12th Street. A project
description is provided below.
PROJECT DESCRIPTION
215 SW 12th Street proposes for a 4,460 square foot addition to an existing auto dealership
located in the city of Renton. The dealership is located at 215 SW 12th Street, with the addition
occurring to the southwesterly portion of the building. The development proposal entails and
expansion of the current service department on-site. The existing dealership is located on a
cumulative 1.63-acres within tax parcel #’s: 334040-2820; 2850; -2860; -2870; & -2885. Access is
to existing dealership is to remain via SW 12th Street and SW 13th Street. A vicinity map of the
surrounding roadway network is provided below with the subject parcel highlighted in blue. A
conceptual site plan is presented in Figure 2 on the following page.
Figure 1: Aerial Vicinity
HEATH & ASSOCIATES, INC Transportation and Civil Engineering
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Figure 2: Site Plan
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TRIP GENERATION
Trip generation is defined by the number of vehicular movements that enter or exit a site during a
particular timeframe. For the proposed uses, estimated trip rates were derived from the Institute of
Transportation Engineer’s publication Trip Generation, 11th Edition. Land Use Code (LUC) 840 –
Automobile Sales (New) was determined to be most representative for the proposed addition.
Square footage was used as the independent variable and average rates were applied to
determine trip ends. Volumes for the average weekday daily trips (AWDT), AM peak hour and PM
peak hour trips are summarized in Table 1 below.
Table 1: Project Trip Generation
Land Use Size AWDT AM Peak-Hour Trips PM Peak-Hour Trips
In Out Total In Out Total
Auto Sales (New)
– LUC 840 4,460 sq. ft. 124 6 2 8 4 7 11
Based on ITE data, the project is anticipated to be a moderate generator of new traffic with 124
average weekday daily trips, 8 AM peak hour trips (6 inbound/2 outbound) and 11 PM peak hour
trips (4 inbound/7 outbound).
The City of Renton thresholds for requiring a Traffic Impact Analysis (TIA) are: 20 new peak hour
trips or 200 new average daily trips. Upon review of the development proposal and ITE data, the
TIA threshold criteria are not met.
TRIP ASSIGNMENT AND DISTRIBUTION
Trip distribution describes the process by which project generated trips are dispersed on the street
network surrounding the site. Trips generated by the project are expected to follow the general trip
pattern as shown in Figure 3 for the PM peak travel hour. Percentages are primarily based on
existing traffic volumes and proximity to nearby arterials/amenities. All project-generated traffic
was assigned to the primary access intersection of SW 12th Street & Maple Avenue SW.
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SUMMARY
215 SW 12th Street Brotherton Cadillac project proposes for the construction of a 4,460 square
foot addition to their service department located in the city of Renton. The 1.63-acre property is
bordered to the north by SW 12th Street and to the west by Maple Avenue SW. The existing
dealership on-site is to remain and access is to continue as currently configured. Based on ITE
data, 8 new AM peak hour trips, 11 new PM peak hour trips and 124 new average weekday daily
trips can be expected coming to and from the site. The project as proposed does not meet the
City’s minimum threshold for requiring a full Traffic Impact Analysis.
Please feel free to contact me should you require further information.
Aaron Van Aken, P.E. PTOE
PO Box 397 Puyallup, WA 98371 (253) 770 1401 heathtraffic.com
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Automobile Sales (New)
(840)
Vehicle Trip Ends vs:1000 Sq. Ft. GFA
On a:Weekday
Setting/Location:General Urban/Suburban
Number of Studies:18
Avg. 1000 Sq. Ft. GFA:36
Directional Distribution:50% entering, 50% exiting
Vehicle Trip Generation per 1000 Sq. Ft. GFA
Average Rate Range of Rates Standard Deviation
27.84 14.98 - 41.78 7.01
Data Plot and Equation
T = Trip EndsX = 1000 Sq. Ft. GFA
Study Site Average RateFitted Curve
Fitted Curve Equation: T = 28.65(X) - 29.45 R²= 0.80
Trip Gen Manual,11th Edition Institute of Transportation Engineers
0 20 40 60 800
500
1,000
1,500
2,000
2,500
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Automobile Sales (New)
(840)
Vehicle Trip Ends vs:1000 Sq. Ft. GFA
On a:Weekday,
Peak Hour of Adjacent Street Traffic,
One Hour Between 7 and 9 a.m.
Setting/Location:General Urban/Suburban
Number of Studies:35
Avg. 1000 Sq. Ft. GFA:30
Directional Distribution:73% entering, 27% exiting
Vehicle Trip Generation per 1000 Sq. Ft. GFA
Average Rate Range of Rates Standard Deviation
1.86 0.59 - 6.17 0.94
Data Plot and Equation
T = Trip EndsX = 1000 Sq. Ft. GFA
Study Site Average Rate
Fitted Curve Equation: Not Given R²= ****
Trip Gen Manual,11th Edition Institute of Transportation Engineers
0 20 40 60 800
50
100
150
200
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Automobile Sales (New)
(840)
Vehicle Trip Ends vs:1000 Sq. Ft. GFA
On a:Weekday,
Peak Hour of Adjacent Street Traffic,
One Hour Between 4 and 6 p.m.
Setting/Location:General Urban/Suburban
Number of Studies:50
Avg. 1000 Sq. Ft. GFA:34
Directional Distribution:40% entering, 60% exiting
Vehicle Trip Generation per 1000 Sq. Ft. GFA
Average Rate Range of Rates Standard Deviation
2.42 0.94 - 5.81 0.98
Data Plot and Equation
T = Trip EndsX = 1000 Sq. Ft. GFA
Study Site Average RateFitted Curve
Fitted Curve Equation: T = 1.81(X) + 20.91 R²= 0.57
Trip Gen Manual,11th Edition Institute of Transportation Engineers
0 20 40 60 800
100
200
300
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CONCEPTSITE PLAN217 SW 12th Street
Renton, WashingtonCOPYRIGHT 2021STATE OF WASHINGTONJAMES H. CASTINOSTATE OF WASHINGTONREGISTEREDARCHITECTREGISTEREDARCHITECT5438PrincipalJames CastinoBrotherton Buick-GMC
SERVICE DEPARTMENT ADDITION8911 71st Ave. NWGig Harbor, WA 98332PHONE: (253) 973-6680EMAIL: jimpilot22@gmail.comPO Box 397 Puyallup, WA 98371 (253) 770 1401 heathtraffic.com 10