When will WSDOT take care of the Highway 18 chokepoint?

Oct 20, 2016, 8:30 AM | Updated: 12:31 pm

Highway 18 at I-90 is one of the most congested interchanges in the state. It’s also one of the spots that generate the most comments from our drivers.

When is the state going to address it?

I recently received a note from Christine, who has been driving Highway 18 for 20 years. She can’t believe how little has been done to handle the increasing traffic over that time. She writes about several near-misses in the backups.

Christine, like many others, wants to know if the state has any plans to address this interchange.

Related: This is guaranteed to cause months-long chokepoint

Sarah Ott, traffic engineer with the Washington State Department of Transportation, says the problem with the Highway 18 / I-90 interchange is obvious.

“There’s just an overwhelming volume heading into the interchange in both the a.m. and p.m. peak hours,” Ott said. “There’s more demand than capacity. We need to add capacity to the interchange.”

Most drivers are quick to blame the traffic lights at Snoqualmie Ridge and at the ends of the freeway ramps, but those are continually tweaked to promote the best flow.

Kris Olsen with WSDOT says there’s not much more they can do.

“Our traffic engineers have manipulated the lights and changed them as much as they possibly can to get them at optimal flow in every direction,” Olsen said.

“The bottom line is until we can rebuild this interchange there’s only so much we can do to get cars through,” she said. “We’ve got more cars than we have room.”

The state has added new signs, created dedicated exit lanes on I-90, but it’s just not enough.

A full Highway 18 interchange remodel is necessary and on the way, just not in the timeframe drivers will like.

“We have $150 million of funding from the Connecting Washington package, however, that does not become available to us to begin design work until 2023,” Olsen said.

Olsen says that calendar is set by the Legislature, not by WSDOT. If you want this interchange fixed faster, you’re going to have to convince Olympia.

“Everybody wants theirs done first,” Olsen said. “Unfortunately, we can’t do them all first. The Legislature — when we got the Connecting Washington package — they divided up the money over the 16-year period and not everybody’s fell where they wanted it to be.”

The state recently put up “no U-Turn” signs on Highway 18 between the two ramps on I-90. Apparently, a lot of drivers have been getting off I-90 by-passing the long backups in the exit lanes and pulling a U-Turn. Now that there is signage, the Washington State Patrol can start ticketing that behavior.

The problem with putting in short-term fixes is that this interchange is an environmental nightmare. There are protected streams right next to the roadway and the exits. Any fix, other than a complete re-design, would be cost prohibitive considering the environmental mitigation that would be necessary.

Send Chris a traffic tip at @KIROTraffic on Twitter or email him.


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When will WSDOT take care of the Highway 18 chokepoint?