New Exit Open, I-90 West Traffic Stuck for Months

New Interchange Fails to Alleviate Congestion on First Weekend

The state’s newest interchange, located at I-90 and State Route (SR) 18 in Snoqualmie, opened last Friday. However, it did not provide much relief during its first weekend. Drivers reported that the usual congestion persisted, particularly during Sunday afternoons.

On Sunday afternoon, many drivers were observed approaching the new Diverging Diamond Interchange (DDI) at SR 18. The goal was to see if the new design and increased capacity would help reduce the long backups that often occur on Sundays. Unfortunately, the results were not as expected.

Brian Nielson, the Regional Administrator for the Washington Department of Transportation (WSDOT), acknowledged that the Sunday afternoon commutes will remain challenging in the area for some time. “Those Sunday afternoon commutes are still going to be challenging in the neighborhood,” he said. He explained that the construction work is still ongoing and that the pinch point is located just south of the interchange.

“We have to finish this widening first,” Nielson added. “The pinch point is really just south of the interchange, so until we finish that this fall, people should probably expect to see congestion through the interchange.”

Despite the current challenges, the new interchange has introduced two lanes of westbound I-90 that now exit to SR 18. This change is expected to help with the Sunday afternoon backup once the widening is completed. It should also reduce late merging issues.

What makes the DDI unique is its design. When exiting to westbound SR 18, drivers turn immediately into the left lanes, which are the opposite lanes of traffic. While this design is smooth, it may be confusing for first-time users.

Improving Safety and Traffic Flow

The Washington State Patrol (WSP) sees the new interchange as an opportunity to improve safety. Lieutenant Pete Cozzitorto, from the WSP, expressed hope that the project would lead to a reduction in congestion. “We’re thankful for this project, and we’re hoping to see a reduction of congestion,” he said. “We’d like to see traffic moving further, faster and allow people to get to where they want to be.”

Most drivers are expected to experience a slight learning curve when using the DDI. However, this should not last long. “It’s gonna be new for a week or two, or the first couple times you go through there, but we expect, all in all, a better commuter experience with this interchange,” Cozzitorto said.

He also hopes that the new design will reduce instances of late merging, road rage, and frustration. “I’m hopeful, with the two lanes exiting off of Interstate 90, that’s going to take some of the congestion off that right lane being stopped as people tried to exit in the past,” he added. “I think with this interchange having more capacity, we’re going to hopefully see a reduction in that congestion.”

Ongoing Work and Future Improvements

WSDOT still has some paving and permanent striping to complete at the interchange. There will be some closures as this work is finished. Once the widening on SR 18 is done, there will be about four miles of two lanes south of I-90 to help ease up to the single lane at Tiger Mountain. This should significantly reduce the slowing on westbound 90.

The contractor is still on schedule to finish the widening this fall. Chris Sullivan, a traffic reporter for KIRO Newsradio, has been covering the developments related to the interchange. Readers can find more of his stories online, and they can follow KIRO Newsradio traffic updates on social media platforms.