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SR 12 Chehalis Safety Study

In collaboration with the Chehalis Tribe, Washington State Department of Transportation (WSDOT), Thurston County, and Grey’s Harbor County, KAI developed near- and long-term safety improvement plans for a five-mile section of State Route 12 in Washington State. KAI applied AASHTO’s Highway Safety Manual (HSM) to evaluate the existing and projected future safety performance of the corridor.

Based on field visits and initial HSM analysis, KAI identified and analyzed potential safety improvements using information and principles from the HSM; FHWA’s CMF Clearinghouse; NCHRP Report 613 Guidelines for the Selection of Speed Reduction Treatments at High Speed Intersections; and FHWA’s Low Cost Safety Concepts for Two-Way Stop Controlled, Rural Intersections on High-Speed Two-Lane, Two-Way Roadways report. Using these resources, KAI calculated the potential crash reduction and planning-level cost estimates to assess the relative cost-effectiveness for each candidate improvement. KAI used these analysis results to develop the near- and long-term safety plans for the corridor.

Two key elements that made this study successful were: 1) Conducting multiple collaborative team work sessions in which the overall team reviewed interim findings and contributed ideas for potential improvements; and 2) Developing a continuum of safety improvements the agencies could implement over time based on their collective resources. The final report provided clear direction on where and how to apply potential improvements to the corridor, while providing flexibility for the agencies to exercise their local knowledge and judgment on when and which improvements to implement.