HomeMy WebLinkAbout2020-04-30 Roadway Proportionate Share Study
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MEMORANDUM
DATE: March 25, 2020
TO: Erika Bowen, P.E.
Idaho Transportation Department
CC: Mark Schultz
Schultz Development
FROM: Chhang Ream, P.E., PTOE
CR Engineering, Inc.
PROJECT: Tanner Creek Subdivision
Meridian, Idaho
SUBJECT: Proportionate Share Calculation – Meridian Road IC to Eagle Road IC Auxiliary Lanes
This memorandum summarizes the proportionate share calculation for Tanner Creek Subdivision on the I-84
auxiliary lane improvements between Meridian Road interchange (IC) and Eagle Road IC. Table 1 summarizes the
traffic data and proportionate share calculation. Based on the 2025 build-out year total traffic volumes, the
proportionate share of Tanner Creek Subdivision is $144,901.
Table 1 – Proportionate Share Calculation Summary
Ramp
2018
Existing Traffic
2025
Background Traffic
2025
Site Traffic
2025
Total Traffic
AM PM AM PM AM PM AM PM
Meridian IC WB Off-Ramp 960 1,901 1,065 2,110 15 50 1,080 2,160
Meridian IC EB On-Ramp 965 580 1,071 644 46 32 1,117 676
Eagle IC WB On-Ramp 6,244 1,484 6,930 1,647 2 5 6,932 1,652
Eagle IC EB Off-Ramp 1,250 1,042 1,387 1,156 5 3 1,392 1,159
Total 14,426 16,011 158 16,169
Average % Site Traffic 0.98%
ITD Improvement Costs Estimate $14,785,782
Tanner Creek Subdivision Proportionate Share $144,901
The following sections discuss the proposed development and traffic data.
181 East 50th Street
Garden City, ID 83714
(208) 841-4996
3/25/20
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Proposed Development & Site Traffic
Tanner Creek Subdivision is an approved residential development located on Waltman Lane in the northwest corner
of the Meridian Road interchange in Meridian, Idaho. A traffic impact study was completed for the project on
November 8, 2017. Figure 1 shows the current development site plan. The current site plan contains 128 single-
family units and 272 apartment units with an expected 2025 build-out year.
The development will have access to the transportation system via a connection to Ruddy Drive at the western site
boundary, a connection to Corporate Drive to the north, and via Waltman Lane to the east.
Figure 1 – Site Plan
I-84 EB
Waltman Ln
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Table 2 summarizes the build-out site trip generation based on the 10th Edition of the ITE Trip Generation Manual
and proposed land uses. Tanner Creek Subdivision is estimated to generate 2,786 trips per day, 187 AM peak hour
trips, and 245 PM peak hour trips.
Site traffic was distributed and assigned to the transportation system similar to the original study. The Linder Road
overpass is not expected to be constructed by the build-out year of this development and was not considered in the
site traffic distribution patterns. Approximately 10% of the site traffic expected to have origins/destinations west of
the site and use the Ruddy Drive connection. Approximately 18% of the site traffic is expected to travel on the
Corporate Drive connection to the north, and approximately 72% of the site traffic is expected to travel through the
Waltman Lane and Meridian Road intersection. Approximately 53% of the site traffic is expected to travel through
the Meridian Road interchange. Figure 2 summarizes the estimated site distribution patterns and peak hour volumes
at the Waltman Lane and Meridian Road intersection and Meridian Road interchange.
Table 2 – Build-Out Trip Generation Summary
2025 Build-Out Year Traffic & Improvements Costs
No new traffic counts were collected for this analysis. 2018 existing counts at the Meridian Road and Eagle Road
interchanges were provided by ITD. The cost estimate for the I-84 auxiliary lane improvements was also
provided by ITD.
To obtain 2025 background traffic, the existing counts were extrapolated with a 1.5% annual growth rate. This
growth rate is consistent with the COMPASS forecasts.
Single-Family Detached Housing 210 128 DU 1,305 50%652 50%653
Multifamily Housing (Mid-Rise)221 272 DU 1,481 50%741 50%740
2,786 1,393 1,393
Single-Family Detached Housing 210 128 DU 96 25%24 75%72
Multifamily Housing (Mid-Rise)221 272 DU 91 26%23 74%68
187 47 140
Single-Family Detached Housing 210 128 DU 129 63%81 37%48
Multifamily Housing (Mid-Rise)221 272 DU 116 61%71 39%45
245 152 93
Weekday Daily (vpd)
Land Use
ITE
Code Size Unit
Total
Trips
Primary Trips
Entering Exiting
Weekday Daily Total Trips
Weekday AM Peak Hour (vph)
Weekday AM Peak Hour Total Trips
Weekday PM Peak Hour (vph)
Weekday PM Peak Hour Total Trips
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Figure 1 – Estimated Site Traffic Distribution Patterns & Peak Hour Site Traffic
5 0 0 14 14 46
14 0 5 15
13 4 0 0
74 0 0 0
25 0 0 AM 0 5 0 AM
15 0 0 9 9 32
9 0 15 50
8 14 0 0
50 0 0 0
80 0 0 PM 0 15 0 PM
Meridian Rd Interchange
Waltman Lane & Meridian Road
Waltman Lane & Meridian Road
Meridian Rd Interchange1
1
2
2
1
2 33%
18
%
10
%
10
%
10%
9%
10%
72%
53
%
I-84 EB
Waltman Ln
Corporate Dr Meridian Rd