Washington State Department of Transportation’s State Route 509, I-5 to 24th Avenue S – New Expressway Project used a practical design approach to advance a long-planned regional expressway and close a critical gap in the freight corridor connecting Interstate 5 and the Port of Seattle. The project improves safety, mobility, and multimodal access for travelers and communities in south King County.

The $267 million project completed the first mile of the planned three-mile corridor and included targeted improvements to I-5 that strengthen regional connectivity and transportation system performance. Enhancements such as ADA-compliant sidewalks, shared-use paths, and trails provide safer connections to schools, jobs, transit services, and recreational destinations.

Variable tolling offers a faster and more reliable route to Seattle’s ports, supporting freight movement and economic activity while preserving toll-free options on many local roadways. The project also included new Veterans Drive tunnels beneath I-5 to reduce congestion and improve local access. In partnership with Sound Transit, WSDOT installed noise walls designed to lessen noise from both the highway and the adjacent light rail line.

With more than 30,000 daily freight trips serving Seattle’s ports, the completed expressway is expected to deliver significant travel-time savings and operational benefits. By improving access, reducing congestion, and strengthening connections between communities and key economic centers, the project enhances supply-chain efficiency and supports the region’s manufacturing, industrial, and freight sectors.