• Project

I-90 – SR 18 Interchange Improvements

The State Route 18 center turn lane at the Interstate 90 interchange was eliminated and the westbound SR 18 lanes were shifted to the west to create a safe work zone on the west side of the interchange. This change will remain in effect until the new diverging diamond interchange opens in late 2024. People traveling on eastbound and westbound SR 18 through the area should avoid distractions and watch for turning vehicles yielding to oncoming traffic.

Project overview

Growth in Snoqualmie Valley has made the I-90/SR 18 interchange one of the busiest in the state, causing backups during peak times and busy travel weekends. To improve traffic flow, WSDOT is building a diverging diamond interchange and adding two lanes on SR 18 between the interchange and Deep Creek.

2022 - 2025
Project status
$188 million
Project hotline

What to expect

Building the diverging diamond interchange and widening SR 18 will be accomplished through several stages of construction during which travelers can expect traffic shifts, speed reductions and intermittent lane and ramp closures throughout the life of the project.

Congestion will increase during construction, so people should plan extra time for trips or find alternative routes.

Reconstructing the I-90/SR 18 interchange will improve safety performance and travel times on I-90, SR 18 and Snoqualmie Parkway.