In 2003, the Washington State Department of Transportation completed the preliminary design and environmental impact study with a record of decision (ROD) for the completion of a missing freeway link - connecting SR 509 to I-5, on the south side of SeaTac International Airport. The project is expected to provide additional access to the Sea-Tac International Airport and the Port of Seattle, provide congestion relief on local arterials and greater opportunity for stimulating economic development. Despite many years of cooperation between WSDOT and its local partners, funding for constructing the project has never materialized due to high project cost (over $1.2 billion) and many other competing projects in the region. The state has been looking at tolling as a potential funding option for this project. Tolling would not only generate revenue, it would also help manage travel demand. This would provide an opportunity to phase construction and reduce initial project costs.

What is the best way to phase the project that will be agreeable to all parties interested in the project? WSDOT decided to answer this question with the help of “Transportation for Communities – Advancing Projects through Partnerships (TCAPP)” developed by Transportation Research Board under the second Strategic Highway Research Program (SHRP 2). TCAPP a decision support tool to systematically build collaboration into transportation decision-making by ensuring the right people are at the table at the right time with the right information to make good choices that will stand up to scrutiny. After working collaboratively with the stakeholders using the tools and techniques provided under the TCAPP corridor planning tool, WSDOT successfully defined Phase 1 of the project. The resulting design reduced the initial project implementation cost by approximately $400 million while preserving most of the project benefits.

This paper documents how the TCAPP tool helped facilitate the project stakeholders and local partners in defining scope of the first phase of the project by taking tolling into consideration, how the TCAPP tool was used to reach collaborative decisions, what information was used from the tool, as well as findings and recommendations for improving the tool.