Appendix D Traffic Impact Analysis - westplainseis.com

In lieu of the various mitigations for the HWY 2/Hayford intersection proposed in the TIA it is
recommended that the Spokane Tribe commit to contributing a proportional share to construction of this
future facility at such time it is programmed for construction. The proportional share contribution should
be based on the proportion of Spokane Tribe site traffic expected to use the facility compared to the
facility capacity.
Revised Analysis/Mitigation at HWY 2/Fairchild AFB Intersection – 2032 Cumulative Conditions
The analysis and recommended mitigation for the HWY 2/Fairchild AFB intersection has been revised
for all 2032 Cumulative analysis scenarios. The recommended mitigation calls for modification of the
northbound approach to include a 2 nd NB right turn lane along with associated modifications to the traffic
signal system. The analysis results for the three alternatives with mitigation are as follows:
1. Alternative 1: LOS D (51.6 secs delay)
2. Alternative 2: LOS D (44.8 secs delay)
3. Alternative 3: LOS D (42.7 secs delay)
SYNCRHO analysis output reports are included in the attachment.
Approach to Traffic Mitigation
The TIA identified mitigations for intersections and roadway facilities that did not meet the prescribed
minimum LOS criteria. For off-site locations, the TIA recommended proportional share contributions
that the project should make toward the indentified mitigation. Both WSDOT and Spokane County staff
have expressed concern regarding proportional share contributions because there unlikely to be available
funding sources to pay for the balance of the project costs beyond the Spokane Tribe’s contribution.
In lieu of a proportional share contribution the Spokane Tribe is proposed to fully fund and/or construct
certain improvements at the time they deemed necessary. In general the strategy is to construct key
mitigations that are most closely related to the impacts caused by the Spokane Tribe project and that will
provide an immediate transportation benefit and added capacity to serve the subject project as well
benefit regional traffic. By constructing the improvements instead of providing partial funding for some
future project or improvement, immediate transportation benefit is provided. Furthermore, the
recommended mitigations discussed will provide a viable and immediately available alternative route to
Spokane Tribe site along Craig Rd. to SR 902 and I-90 which may serve to relieve traffic along HWY 2.
The proposed mitigations by Site Plan Alternative and Project phase are summarized below.
Alternative 1
2012 (Phase 1) Mitigations:
HWY 2 - Craig Rd. to Westerly Project Site Property Line: Construct a roundabout at the Craig
Rd. intersection and two site access intersection with roundabout intersection control generally at
the locations identified in Attachment A. Construct frontage improvements along the northerly
side of HWY 2 including curbing, drainage improvements, sidewalks or paths as applicable.
(Note the proportional share responsibility for the Craig Rd. intersection was calculated as 34.2%
in the TIA)
Resulting LOS & Delay (sec):
HWY 2 / Craig: A/7.8
HWY 2 / East Site Access: B/15.2
West Plains Development – Spokane Tribe Page | 4
Traffic Impact Analysis Addendum July 18, 2011