The first mile of the new SR 509 Expressway in SeaTac will open to drivers at the appropriate time of 5:09 a.m. this Saturday, June 28, 2025, marking a major milestone in the multi-year SR 509 Completion Project, according to the Washington State Department of Transportation (WSDOT).
The new stretch connects northbound I-5 to 24th Avenue South via a large fly-over ramp, providing a new option for travelers moving through SeaTac.
The full three-mile corridor, running between I-5 and South 188th Street, is expected to be completed by 2028.
“This first mile is a critical step toward completing the corridor,” WSDOT said in a statement.
Tolling Begins in the Fall
For now, the expressway will be free to use, but tolling is set to begin in the fall to help pay for construction and ongoing maintenance.
Until the next section opens, drivers will exit at 24th Avenue South.
Travelers can also enter the expressway from 24th Avenue South to merge onto southbound I-5.
What are the railroad crossing bars for, that are located on the east and west side of the tunnel going under the runway?
I would assume for some sort of emergency on the runway directly above a roadway that would be dangerous for vehicles to use the underpass.
Even though it’s not going to connect 509 to I-5 for 3 more years they are tolling what is essentially and I-5 off ramp/on ramp for 24th Ave!? Does WSDOT think that people won’t drive an extra couple of minutes to use the 200th street interchange for free.