After years of preparation, WSDOT widens northbound I-5 into downtown Seattle

Mar 24, 2022, 5:42 AM

I-5, Seattle...

A view of downtown Seattle. (Flickr Creative Commons)

(Flickr Creative Commons)

The Washington State Department of Transportation has been preparing us for this project for more than a few years: the widening northbound I-5 into downtown Seattle. And this is the year it’s finally happening.

There was a nighttime closure of northbound I-5 Wednesday, and there will be another one Thursday. These are the opening moves in the construction that will add another 1,500 feet of lane through downtown Seattle.

All traffic will be detoured into the downtown collector-distributor lanes from 9 p.m. to 5 a.m. Thursday. WSDOT’s Tom Pearce said they need the room to begin moving barriers to squeeze out the space for the new lane between Seneca and University Street.

“Just for the safety of the construction workers, we need to close the mainline lanes sometimes because they’re out there removing barriers, building the new barriers, and re-striping so we need to have plenty of room for them to do it safely,” Pearce said.

The state is turning the Seneca Street off-ramp from an exit-only lane to an optional exit and through lane. That will give drivers three northbound lanes going under the Convention Center.

“Not having people merge at the last second, it’s really going to make a difference on the flow of traffic going northbound,” Pearce said. “Everybody bunches up there, especially when the express lanes are southbound.”

Two through lanes will become three through lanes. Added capacity — that’s a good thing for drivers.

The other part of this project might not be so welcome, especially for drivers using westbound I-90 to northbound I-5. The state is adding ramp meters to the collector-distributor lanes, which means drivers heading from I-90 to northbound I-5, and those heading north from the stadiums, will face managed queues.

“We’re going to have two lanes on the collector-distributor with ramp meters, and then they’ll alternate the traffic to keep the flow going well onto the mainline,” Pearce said. “That’s also going to provide us some more space to collect the vehicles when we do get some backups.”

There will also be a new ramp meter from Cherry Street.

Drivers need to be ready for more lane closures as this project progresses.

Check out more of Chris’ Chokepoints.



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After years of preparation, WSDOT widens northbound I-5 into downtown Seattle