23-103436-UP-Trip Generation Assessment-07-25-2023HeathTraffic.com
June 27, 2023
City of Federal Way
Kathy Davis, P.E., PTOE
Public Works Traffic Division
Subject: Trip Generation Assessment – 348th Commercial
Heath & Associates has been retained to prepare a Trip Generation Assessment for
the proposed development herein referred as 348th Commercial. The intent of this
assessment is to provide the city with a trip generation summary to be used in concert
with the Concurrency Application. A project description is provided below.
PROJECT DESCRIPTION
· 348th Commercial is a proposed commercial building comprised of 6,339
square feet located within the city of Federal Way.
o No tenant or use for the commercial building is known at this time.
o The building could contain a single tenant of divisible for up to three
tenants.
· The subject site, 1420 S 348th Street, is bordered to the south by S 348th
Street, east of Pacific Highway S and west of west of 16th Avenue S situated on
0.96-acres within tax parcel #: 202104-9088.
o An existing 5,256 square foot commercial retail exists on-site and is to
remain.
o The proposed building would be constructed west of the existing
building.
· Access to the site will continue via two right-in/right-out driveways S 348th
Street.
· A vicinity map is provided on the following page with the subject site
highlighted in blue. A conceptual site plan is presented in Figure 2.
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348th Commercial Trip Generation Assessment
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SITE LOCATION
Figure 1: Vicinity Map
N
S 348th St 16th Ave S
FIGURE 2
SITE PLAN
348TH COMMERCIAL
N
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348th Commercial Trip Generation Assessment
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TRIP GENERATION
The magnitude of the anticipated vehicle trip generation for the proposed project
was derived from the Institute of Transportation Engineers (ITE) publication, Trip
Generation Manual, 11th Edition. Currently, the “shell” commercial building has no
known tenants. Tenant occupancy is predicated on market demands and could be a
single tenant or up to three separate tenants. Given the variety of potential uses, ITE’s
LUC 822 – Strip Retail (<40K) was determined most representative for determining
trip forecasts. Average rates were applied against the building’s 6,339 square feet.
Trip Generation Adjustments
Pass-By
Pass-by trips have been considered for this project. Pass-by trips, or motorists already
passing by the site who decide to make an intermediate stop, are common among
commercial/retail services. These trips are not considered as new trips but will impact
the site’s access points. ITE reports a 40% pass-by rate for LUC 821(similar use) which
will be applied. Given the restricted accesses (right-turns only) and the high volumes
along S 348th Street with visibility, pass-by rates could conceivably be higher.
Table 1: Project Trip Generation
Land use Size Trip
Type AWDT AM Peak-Hour Trips PM Peak-Hour Trips
In Out Total In Out Total
LUC – 822
Retail 6.339 ksf
Primary
(60%) 207 6 3 9 12 13 25
Pass-By
(40%) 138 3 3 6 9 8 17
Total Trips 345 9 6 15 21 21 42
Based on the data above, the project is anticipated to generate 207 primary average
weekday daily trips with 9 primary AM peak hour trips (6 inbound/3 outbound) and
25 primary PM peak hour trips (12 inbound/13 outbound). ITE trip generation sheets
have been attached to the appendix for reference.
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348th Commercial Trip Generation Assessment
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SUMMARY
The 348th Commercial project proposes for the construction of a 6,339 square foot
commercial building that could accommodate between one to three different
tenants. The subject site is located within the city of Federal Way situated on 0.96-
acres on tax parcel: 202104-9088. Based on ITE’s data, LUC 822 – Strip Retail was
found most representative of the project.
The estimated new trips from the project are 207 daily trips with 9 trips occurring in
the AM peak hour and 25 trips in the PM peak hour.
2525
0
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348TH COMMERCIAL
TRIP GENERATION ASSESSMENT
APPENDIX
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Strip Retail Plaza (<40k)
(822)
Vehicle Trip Ends vs:1000 Sq. Ft. GLA
On a:Weekday
Setting/Location:General Urban/Suburban
Number of Studies:4
Avg. 1000 Sq. Ft. GLA:19
Directional Distribution:50% entering, 50% exiting
Vehicle Trip Generation per 1000 Sq. Ft. GLA
Average Rate Range of Rates Standard Deviation
54.45 47.86 - 65.07 7.81
Data Plot and Equation Caution – Small Sample Size
T = Trip EndsX = 1000 Sq. Ft. GLA
Study Site Average RateFitted Curve
Fitted Curve Equation: T = 42.20(X) + 229.68 R²= 0.96
Trip Gen Manual,11th Edition Institute of Transportation Engineers
0 10 20 30 400
500
1,000
1,500
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Strip Retail Plaza (<40k)
(822)
Vehicle Trip Ends vs:1000 Sq. Ft. GLA
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:5
Avg. 1000 Sq. Ft. GLA:18
Directional Distribution:60% entering, 40% exiting
Vehicle Trip Generation per 1000 Sq. Ft. GLA
Average Rate Range of Rates Standard Deviation
2.36 1.60 - 3.73 0.94
Data Plot and Equation Caution – Small Sample Size
T = Trip EndsX = 1000 Sq. Ft. GLA
Study Site Average RateFitted Curve
Fitted Curve Equation: Ln(T) = 0.66 Ln(X) + 1.84 R²= 0.57
Trip Gen Manual,11th Edition Institute of Transportation Engineers
0 10 20 30 400
20
40
60
80
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Strip Retail Plaza (<40k)
(822)
Vehicle Trip Ends vs:1000 Sq. Ft. GLA
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:25
Avg. 1000 Sq. Ft. GLA:21
Directional Distribution:50% entering, 50% exiting
Vehicle Trip Generation per 1000 Sq. Ft. GLA
Average Rate Range of Rates Standard Deviation
6.59 2.81 - 15.20 2.94
Data Plot and Equation
T = Trip EndsX = 1000 Sq. Ft. GLA
Study Site Average RateFitted Curve
Fitted Curve Equation: Ln(T) = 0.71 Ln(X) + 2.72 R²= 0.56
Trip Gen Manual,11th Edition Institute of Transportation Engineers
0 10 20 30 400
100
200
300