New Dedicated Transit Lane Planned For Seattle-Eastside Commuters

REDMOND, WA — In a few years, transit riders that commute between South Lake Union and the Eastside should have faster trips in both directions, using a new dedicated and reversible express lane connecting Interstate 5 and Mercer Street with State Route 520.

The Washington State Department of Transportation announced the project Monday, with plans to begin construction this summer. Once completed, it will extend SR 520's transit and HOV lanes, directly linking to the Mercer Street interchange using the I-5 express lanes.

According to WSDOT, six contractors bid on the project, with Walsh Construction securing the project for $68 million, coming in with the lowest bid at less than the state's estimate.

"We're excited to work with Walsh to build this next piece of the SR 520 Program," said Omar Jepperson, a program administrator for WSDOT. "When complete, this project will provide a reliable transit link between the region's major employment centers in Seattle's South Lake Union and the Eastside."

When express lane traffic is running southbound, the new ramp will connect to westbound 520. When traffic is running northbound, the ramp will connect for eastbound trips across Lake Washington. At first, the new dedicated lane will be transit-only, with plans to open for carpools after the new Roanoke Lid Project is complete.

Here's how it works:

Construction work on the new connection is slated to begin in the summer and be completed toward the end of 2023.

These are the three major components of the project:

• Building a new, reversible transit/HOV ramp between SR 520 and the I-5 express lanes
• Restriping I-5 express lanes to retain the four existing lanes while adding a reversible transit/HOV lane between the I-5/SR 520 interchange and Mercer Street
• Modifying an existing ramp for reversible operations between the I-5 express lanes and Mercer Street

The express lane connection is the second of four planned improvements between I-5 and SR 520. Learn more about the "Rest of the West" improvements on the WSDOT website.