Why a traffic sign is the culprit to creating unnecessary congestion on I-90

The new diverging diamond interchange, where I-90 meets SR 18 in Snoqualmie, was supposed to improve the massive delays drivers have experienced there almost every weekend in the past. Ten months into the change, the delays are still there, and one sign might be to blame.

Getting rid of the two-mile backup on westbound I-90 to westbound SR 18 was one of the key selling points of the new interchange, but those backups haven’t gone away.

“I’m hopeful, with the two lanes exiting off of Interstate 90, that’s going to take some of the congestion off of that, as you mentioned, that right lane being stopped as people tried to exit in the past,” Washington State Patrol (WSP) Lieutenant Pete Cozzitorto said in July 2025 when the interchange first opened. “I think with this interchange having more capacity, we’re going to hopefully see a reduction in that congestion.”

But that hasn’t happened because drivers don’t know that two lanes now exit, and there are no signs to tell them. Charlie Harger, host of “Seattle’s Morning News,” has been through there twice recently, and he told me, “It’s as bad as it’s ever been.”

Why?

I am not a traffic engineer, but the answer seems quite obvious to me. Drivers do not realize that two lanes now exit to SR 18. They are jumping into the far right lane when they don’t have to, creating a massive backup.

Before the new interchange opened, only the far-right lane exited. It was an exit-only lane. You had to be in the right lane. If you weren’t, you forced your way into the lane by cutting people off and darting into the smallest of spaces.

Drivers don’t have to do that anymore. Two lanes exit to SR 18.

Why aren’t drivers getting the message?

It’s likely because there are no signs indicating that both lanes exit. The same old sign reading “West 18, Auburn, 1 mile, exit only” sits above the freeway today. It gives drivers the impression that they have to be in that lane when they don’t have to be. The only sign to clue drivers in that a second lane exits sits right at the exit, almost too late to notice.

Changing that sign to indicate that two lanes exit at SR 18 seems like a reasonable ask, but the Washington Department of Transportation told me there are no plans to add information or change the sign.

That is outside the scope of the current project, the Washington Department of Transportation (WSDOT) told me.

While the exit-only sign is accurate for the right lane, it means drivers must exit the freeway if they’re in that lane, but it’s not the only exit lane available to drivers heading to SR 18.

Until drivers realize that two lanes exit or WSDOT changes the signs, those terrible westbound I-90 backups are not going away. There is no reason to be in that far right lane, unless you want to go up the hill to Snoqualmie. Both lanes access westbound SR 18.

Normally, I would never tell you to ignore a traffic sign, but in this case, it’s the only way to eliminate the backup.

Two right lanes exit, even though the current sign says differently.

Chris Sullivan is a traffic reporter for KIRO Newsradio. Read more of his stories here. Follow KIRO Newsradio traffic on X.

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