All traffic heading to the Eastside from Seattle on Interstate 90 after 11:30 p.m. Friday, Feb. 21, will be diverted to the center roadway express lanes from west of the Mount Baker Tunnel across Mercer Island. The Rainier Avenue on-ramp to eastbound I-90 will be closed as well.

All lanes will reopen by 7 a.m. Saturday.

Access to Mercer Island from the eastbound I-90 express lanes is available at 77th Avenue Southeast and Island Crest Way.

The traffic diversion is necessary for the Washington State Department of Transportation conduct follow-up testing of new technology to upgrade smoke and fire detection, response and safety inside the I-90 tunnels. WSDOT contractor crews will set small, controlled fires in the Mt Baker Tunnel to test a new video-detection system. The fires, set in metal pans up to 4 feet long, will not be visible to traffic. The work is part of the final stage of the I-90 Two-Way Transit and HOV Operations project.