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northbound I-5, Seattle
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WSDOT finally widening northbound I-5 through downtown Seattle

From Yesler Bridge over I-5 looking northward. (Photo courtesy of SDOT/Flickr)

The state is finally addressing one of the biggest chokepoints in our region by widening northbound I-5 through downtown Seattle, but it will come with a cost for people who drive on I-90 and use the downtown collector-distributor lanes.

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The morning I-5 drive into Seattle is one of the worst congestion spots in the state. It routinely backs up about four miles, from before the West Seattle Bridge to the middle of the convention center. There are a variety of reasons for the backup, including that it’s a very popular stretch of freeway. There is also a lot of lane changing and weaving to access the downtown exits, the collector-distributor lanes, I-90, and the Express Lanes.

But it certainly doesn’t help that one lane goes away at Seneca Street. It is an exit only lane that causes another round of lane-changing.

“You go from three lanes to two lanes to three lanes, and the traffic pinches down,” the Washington State Department of Transportation‘s Tom Pearce said.

WSDOT is finally going to make a change. It is going to use the room between the Seneca off-ramp and the on-ramp from University Street to add a lane. It is going to connect those two dots.

“We’re going to go in and fill-in that little 1,500 foot gap,” Pearce said. “Seneca will become a regular off-ramp, but there will also be a through lane there so we end up with three through lanes the entire way on northbound I-5 from I-90 to the convention center.”

Construction on this project is set to begin next month, and Pearce said it will take two summer seasons to finish. The goal is to have this lane open in the fall of 2022.

“We expect that when this section becomes three lanes all the way through that just reduces merges, lane changes,” Pearce said. “That is going to help smooth out the flow of traffic.”

And now to the cost to I-90 and C-D lane drivers that we mentioned at the beginning.

WSDOT has another piece of this downtown I-5 puzzle to place, and it likely won’t make many people happy. Pearce said the state will be installing ramp meters at the end of the C-D lanes to control the flow onto I-5. When the meters are active, westbound I-90 drivers accessing northbound I-5 will be stopped at red lights.

“This project is going to add two lanes that are going to come onto I-5, but we’re going to have ramp meters,” he said. “The two lanes will funnel down to one.”

This will be similar to the Mercer on-ramp to northbound I-5.

Pearce said a ramp meter will also be added at the I-5 northbound on-ramp from Cherry Street, which likely won’t many people happy, but it’s all about controlling the flow.

“This is really going to reduce the urge of drivers to speed up, try and get in front of somebody because you’re really not going to gain much,” Pearce said. “You might gain a car length, and is it really worth racing around to gain one car length?”

The final piece will be an exit only lane to Olive Way.

Pearce knows this will be a big change for drivers, but the goal is to clear out this daily chokepoint and make I-5 a better drive.

Check out more of Chris’ Chokepoints.

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