WSDOT finally widens I-5 northbound through downtown Seattle

The state is finally tackling one of our region’s biggest choke points by widening I-5 northbound through downtown Seattle, but it will come at a cost to people driving on I-90 and use the downtown collector-distributor lanes.

SDOT race to complete the Fairview Avenue Bridge

The I-5 morning trip to Seattle is one of the worst congestion spots in the state. It steadily 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 the fact that this is a very popular stretch of highway. There are also plenty of lane changes and weaves to access downtown exits, collector-distributor lanes, I-90, and expressways.

But it certainly doesn’t help that one lane disappears at Seneca Street. This is an exit-only lane that causes another lane change cycle.

“You go from three lanes to two lanes to three lanes, and the traffic gets tighter,” said the Washington State Department of Transportationsaid Tom Pearce.

WSDOT is finally going to make a change. He will use the room between the Seneca exit ramp and the University Street on-ramp to add a lane. It will connect these two points.

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

Construction on that project begins Monday, and Pearce said it would take two summer seasons to complete. The goal is to open this route in the fall of 2022.

“We expect that when this section becomes three lanes all the way through, it will just reduce merges, lane changes,” Pearce said. “It’s going to help smooth the traffic.”

And now let’s talk about the cost for the I-90 and CD lane drivers we mentioned at the beginning.

WSDOT has another piece of this downtown I-5 puzzle to place, and it probably won’t make a lot of people happy. Pearce said the state will install ramp meters at the end of CD lanes to control throughput on 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 over I-5, but we’re going to have ramp counters,” he said. “The two paths will be reduced to one.”

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

Pearce said a ramp meter will also be added to the north on-ramp of I-5 from Cherry Street, which probably won’t appeal to many people, but it’s all about flow control.

“It’s going to really reduce the drivers’ urge to speed up, to try to get past somebody because you’re really not going to gain much,” Pearce said. “You could win a car length, and is it really worth running to win a car length?”

The last piece will be an exit route only to Olive Way.

Pearce knows this will be a big change for drivers, but the goal is to eliminate that daily choke point and make the I-5 a better ride.

Check out more of Chris’ Chokepoints.