First mile of SR 509 Expressway to open in SeaTac early Saturday

The first mile of the SR 509 Expressway in SeaTac opens to traffic at 5:09 a. m. on Saturday, June 28, 2025. This new segment connects northbound I-5 to 24th Avenue South through a large fly-over ramp, providing an alternative route for travelers. The Washington State Department of Transportation (WSDOT) emphasized that this mile represents a significant advancement in the multi-year SR 509 Completion Project, which is expected to be fully operational by 2028.

Although the expressway will be free to use initially, tolling will commence in the fall to support ongoing construction and maintenance. Until the next section becomes available, drivers will need to exit at 24th Avenue South. This project is anticipated to alleviate congestion and improve accessibility in SeaTac. The opening of the expressway marks a key milestone in regional transportation infrastructure development. WSDOT's efforts aim to enhance travel efficiency in the area.