UPDATE: Repaving work originally scheduled this weekend on the Aurora Bridge has been postponed due to rain in the forecast.

Travelers can expect lane closures and traffic delays on Seattle-area highways this weekend as maintenance and construction season continues full-steam ahead.

The work includes light-rail construction over Interstate 405 and maintenance of the Interstate 90 Mercer Island lid and Mount Baker tunnel.

Congestion is expected to spill into other streets and highways as drivers seek other routes to avoid the closures.

Traffic Lab is a Seattle Times project that digs into the region’s thorny transportation issues, spotlights promising approaches to easing gridlock, and helps readers find the best ways to get around. It is funded with the help of community sponsors Alaska Airlines, Kemper Development Co., NHL Seattle, PEMCO Mutual Insurance Company and Seattle Children’s hospital. Seattle Times editors and reporters operate independently of our funders and maintain editorial control over Traffic Lab content.

Interstate 405

In Bellevue this weekend, crews will begin removing the temporary steel columns and beams that supported construction of a new Sound Transit light-rail bridge over I-405, requiring freeway lane closures.

The bridge is part of the expansion of light rail between Seattle and Overlake, to open in 2023.

Temporary columns and beams that supported the 810-foot light-rail bridge across I-405 while it was under construction will be removed beginning this weekend. Crews will close lanes and ramps on I-405 over two consecutive weekends to do the work.   (Ellen M. Banner / The Seattle Times)
Temporary columns and beams that supported the 810-foot light-rail bridge across I-405 while it was under construction will be removed beginning this weekend. Crews will close lanes and ramps on I-405 over two consecutive weekends to do the work. (Ellen M. Banner / The Seattle Times)

From 10 p.m. Friday to midnight Saturday, the southbound I-405 ramps in Bellevue will be closed. Those include the offramp to Northeast Fourth Street and the Northeast Eighth Street onramp to southbound I-405.

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Then from midnight Saturday until 5 a.m. Monday, all southbound I-405 lanes will be closed between Northeast 10th Street and Main Street. The southbound I-405 HOV offramp to Northeast Sixth Street will also be closed, along with the northbound I-405 HOV offramp and the southbound HOV onramp to and from Northeast Sixth Street.

This view of I-405 looks southbound from the new 810-foot light-rail bridge that crosses the freeway at Bellevue. On a clear day, Mount Rainier is visible at top left.  (Ellen M. Banner / The Seattle Times)
This view of I-405 looks southbound from the new 810-foot light-rail bridge that crosses the freeway at Bellevue. On a clear day, Mount Rainier is visible at top left. (Ellen M. Banner / The Seattle Times)

From 10 p.m. Friday, Aug. 16, until just before midnight Saturday, Aug. 17, the northbound I-405 offramp to Northeast Eighth Street and the Northeast Fourth Street onramp to northbound I-405 will be closed.

And at midnight Aug. 17, all northbound I-405 lanes between Main Street and Northeast 10th Street will close until 5 a.m. Aug. 19. The northbound I-405 HOV offramp and the southbound HOV onramp to and from Northeast Sixth Street will also close.

Drivers will be directed to ramp-route detours and the collector-distributor road during the closures, which are expected to also impact traffic on Highway 520, I-90, Interstate 5 and Bellevue city streets.

Interstate 90

All lanes of westbound I-90 between Mercer Island and Seattle will close from 10 p.m. Friday to 5 a.m. Saturday for inspections and maintenance. The closures include all westbound onramps from Island Crest Way on Mercer Island to I-5 in Seattle.

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WSDOT crews will review safety systems in the Mercer Island Lid as required by the federal government, and also will clean walls, lights and catch basins in the Mount Baker Tunnel.

The same inspection and maintenance is planned on the I-90 eastbound lanes the following weekend, from 10 p.m. Aug. 17 to 5 a.m. Aug. 18.

Meanwhile, WSDOT is also working to create more auxiliary lanes on both directions of I-90 between Eastgate and West Lake Sammamish Parkway as part of a $76 million.

An auxiliary lane is an extra lane that’s added between interchanges to give drivers more time to safely merge at exits and entrances.

The new lanes will be located on the outside of the existing right-hand lanes and will be available to travelers all times of the day.

Contractors must reinforce the shoulders so they can handle the weight of the extra traffic. Crews will temporarily re-stripe both directions of I-90 and shift traffic to install concrete barriers along the outside lanes.

As the work continues, drivers should expect overnight lane and ramp closures between 8 p.m. and 5 a.m., single lane closures during the daytime hours and long-term shoulder closures.

The project is expected to be complete by fall 2021.