I-90/SR 18 Interchange Project Nears Completion, More Closures Expected

Drivers should prepare for extended weekend closures and delays through spring and summer as final phase of project gets underway.

Mar. 30, 2026 at 3:56pm

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A construction project to improve the congested I-90/SR 18 interchange in Washington state is nearing completion, but drivers should expect several more months of disruptions. The next phase of the project will bring overnight closures, lane reductions, and at least three extended weekend closures over the spring and summer as crews complete paving and striping work.

Why it matters

The I-90/SR 18 interchange is one of the busiest highway junctions in the region, and the project aims to ease chronic congestion and backups that have plagued the area for years. While the final phase will bring more short-term disruptions, transportation officials say the completed project will provide long-term relief for this critical travel corridor.

The details

The project has already delivered improvements, including the opening of a diverging diamond interchange last summer that has reduced backups that used to extend onto I-90. However, the final phase will require overnight closures of eastbound SR 18 starting this week, followed by extended weekend closures over the spring and summer to allow for paving and striping work. Drivers are advised to plan ahead, allow extra travel time, and consider alternate routes to avoid the expected congestion.

  • The next phase kicks off with an overnight closure of eastbound SR 18 beginning at 8 p.m. Tuesday, March 31, between I-90 and Issaquah-Hobart Road.
  • In early April, the right lane of eastbound SR 18 will close to allow crews to remove guardrail in preparation for paving, which could begin as early as the evening of April 9.
  • At least three extended weekend closures are scheduled throughout the spring and summer, each lasting from 9 p.m. Thursday through 5 a.m. Monday.
  • The diverging diamond interchange project itself will be complete once paving and striping are finished, with the broader SR 18 widening effort expected to wrap up by late summer.

The players

Marcus Humberg

A spokesperson for the Washington State Department of Transportation (WSDOT).

WSDOT

The Washington State Department of Transportation, the agency overseeing the I-90/SR 18 interchange project.

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What they’re saying

“So it actually really improves the flow of traffic, and we saw that almost immediately when we opened it. Traffic backups that used to extend well onto I-90 in both directions... it's almost gone.”

— Marcus Humberg, WSDOT spokesperson

“We've got basically three long extended weekend closures of the freeway that people are going to have to contend with. We expect there's going to be a lot of traffic, backups, and extended wait times.”

— Marcus Humberg, WSDOT spokesperson

What’s next

Drivers should prepare for at least three extended weekend closures throughout the spring and summer, with the first closure scheduled to begin at 9 p.m. Thursday, April 9 and last through 5 a.m. Monday.

The takeaway

While the final phase of the I-90/SR 18 interchange project will bring more short-term disruptions, the completed improvements are expected to provide long-term relief for one of the region's most congested travel corridors. Drivers should plan ahead, allow extra time, and consider alternate routes to avoid the expected delays.