Southbound I-5 mainline to close in downtown Seattle overnight July 19; traffic will use express lanes

SEATTLE – The southbound Interstate 5 mainline through downtown Seattle will close Friday night, July 19, and all southbound traffic will use the express lanes through early Saturday morning.

Beginning at 11 p.m. Friday, July 19, until 6 a.m. Saturday, July 20, all southbound mainline lanes will close near the Seattle Convention Center for scheduled maintenance. Travelers should plan for extra travel time or take alternate routes during this closure.

During the closure, Washington State Department of Transportation maintenance crews will conduct fire system testing under the Seattle Convention Center.

Closure details

People traveling overnight Friday, July 19, in Seattle should expect all southbound I-5 mainline lanes to close from the Stewart Street off-ramp to the Spring Street on-ramp (about milepost 167 to 165). Any vehicles still on the southbound I-5 mainline will need to exit at Stewart Street. Crews will close one lane at a time to safely set up the work zone. The first lane will close at 9 p.m. and the full closure will begin at 11 p.m. 

Other southbound I-5 ramp closures to begin at 10 p.m. include:

  • Eastbound Mercer Street on-ramp
  • Yale Avenue/Howell Street on-ramp
  • Off-ramp to Union Street
  • Off-ramp to James Street


During the closure, the I-5 express lanes will be open for southbound traffic for those wishing to exit in downtown. A flammable cargo restriction will be in place. The northbound express lanes will close early to accommodate the southbound mainline closure.

The testing beneath the convention center for northbound I-5 will occur overnight July 25 and 26. I-5 will have a lane reduction while crews work, but the express lanes will also be available for use during that closure. While the testing is occurring, a flammable cargo restriction will be in place for I-5 in Seattle.

An unplanned flammable cargo restriction is in place for the Mount Baker and the Mercer Island Lid tunnels on I-90. Currently, there is no estimate for when the I-90 restriction will be lifted. Drivers with flammable cargo will need to seek alternative routes.

People can get real-time traffic information on mobile phones with the WSDOT traffic app and the WSDOT real-time travel map.

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