This map shows the projects that will replace SR 99 through Seattle.

Click this map to see related projects.

Click on the project boxes for more information. Click the X in the corner to close this window

Building a new State Route 99 through Seattle

The Alaskan Way Viaduct, an elevated section of State Route 99 in Seattle, was built in the 1950s, and decades of daily wear and tear have taken their toll on the structure. Because of the viaduct’s age and vulnerability to earthquakes, replacing it is critical to public safety.
The Alaskan Way Viaduct Replacement Program includes projects led by the Washington State Department of Transportation, King County, the City of Seattle and the Port of Seattle. The Federal Highway Administration is a partner in this effort. 

Major elements of the program include:

  • A two-mile-long tunnel beneath downtown Seattle.
  • A mile-long stretch of new highway that connects to the south entrance of the tunnel, near Seattle’s stadiums.
  • A new overpass at the south end of downtown that allows traffic to bypass train blockages near Seattle’s busiest port terminal.
  • Demolition of the viaduct’s downtown waterfront section.
  • A new Alaskan Way surface street along the waterfront that connects SR 99 to downtown.


Our schedule page includes a list of all 30 projects that are led or funded by the state as part of this effort.

Related projects

As part of the Alaskan Way Viaduct Replacement Program, our partner agencies are planning street, transit and waterfront improvements. Click on the related projects map above to learn more.

Halfway there

Half of the viaduct is already gone, demolished and replaced by crews at the south end of downtown, near Seattle’s stadiums. Completed on budget and one year ahead of schedule, this new section of SR 99 connects to the remaining viaduct along the waterfront to keep SR 99 traffic moving until the tunnel opens to traffic.

Changing access

The SR 99 tunnel will change the way traffic uses SR 99 in Seattle. Drivers approaching the tunnel from either direction will face a choice depending on their destination: use the tunnel to bypass downtown or exit to city streets and head into downtown. At the tunnel’s north end, downtown access will be similar to today, with on- and off-ramps near Seattle Center. From the south, new on- and off-ramps will connect SR 99 to downtown via the new waterfront street.

Construction mitigation

We work closely with residents and businesses near the viaduct to help them through construction. Milepost 31, our award-winning project information center, helps attract visitors and business to Pioneer Square. WSDOT’s parking mitigation program focuses on strategies that offset construction-related on-street parking impacts in Pioneer Square and the waterfront neighborhoods.