Buckle up and pay attention, drivers. The first ramps at the Interstate 90/State Route 18 diverging diamond interchange will open this week.

The Washington State Department of Transportation (WSDOT) has been working to improve safety and traffic flow at the interchange since 2022.

Diverging diamond interchanges are designed to eliminate the need for left-turning vehicles to cross the path of approaching vehicles, according to WSDOT. Once complete, the I-90/SR 18 diverging diamond interchange is expected to reduce the number of vehicle conflict points from 26 to 14, and collisions by 50 percent.

“There really isn’t anything new to learn, and striping, signing and signal displays are very effective in routing drivers through the interchange,” the WSDOT website reads. “The lanes funnel drivers where they need to go, and there is only one route to take through the traffic signals with well-marked and easy-to-follow entry and exit points.”

The SR 18/Snoqualmie Parkway on-ramp to westbound 1-90 and the I-90 off-ramp to eastbound SR 18 will be open by Sept. 13.

Nighttime closures are expected on portions of the interchange from Sept. 9 to Sept. 12 as crews work to install overhead structures to hold new signs and switch to the new ramps. Signed detours will be placed accordingly.

The 1-90/SR 18 diverging diamond interchange is expected to be completed in 2025 and will be the second to open in the state.