SR 520 I-5 Express Lanes Connection Project

Plans and process

Over the last decade, Seattle’s population and employment boomed, especially in the South Lake Union neighborhood. At the same time, the Eastside’s technology-driven cities continued to see rapid growth. These two factors underscore the importance of a safe, reliable transit/HOV link between Seattle and the Eastside via SR 520. This project addresses this issue by creating a direct bus and carpool connection from SR 520 to South Lake Union and downtown Seattle.

This project is a central part of the larger, ongoing SR 520 Bridge Replacement and HOV Program to reconstruct the SR 520 corridor from I-405 in Bellevue to I-5 in Seattle. We’ve already completed several phases of the program, including:

• Floating Bridge and Landings Project: Built the world’s longest floating bridge across Lake Washington between Seattle and the Eastside, and constructed the bridge’s 44 smaller pontoons in Tacoma.
• Pontoon Construction Project: Built the floating bridge’s 33 largest pontoons in Tacoma and Aberdeen, Washington.
• Eastside Transit and HOV Project: Rebuilt the highway’s Eastside segment between I-405 and Lake Washington’s east shore.
• West Approach Bridge North Project: Completed the first of two parallel west approach bridges over Union Bay, between the floating bridge and Seattle’s Montlake neighborhood.

The Montlake Project, currently under construction, is completing the second of two parallel west approach bridges over Union Bay. This project includes building a new landscaped lid over the highway, and a bicycle and pedestrian bridge to the east of the lid.

When the corridor’s reconstruction is fully completed in the late 2020s:

• All of SR 520’s major bridges will be replaced with stronger structures.
• The bus/carpool lanes and a regional bicycle and pedestrian path will extend from Seattle east to Redmond
• Travelers will have safer on and off-ramps and improved connections to transit, local streets, and local and regional trail networks.

Project benefit

Safer, more reliable bus and carpool travel between the Eastside, the South Lake Union area, and downtown Seattle through a new, reversible transit/HOV lane that connects SR 520 and the I-5/Mercer Street interchange.

Project design

The SR 520/I-5 Express Lanes Connection Project’s design was developed through years of coordination between WSDOT, the city of Seattle, and partner transit agencies. Visit the Maps and Drawings tab for renderings of key project elements.

High Occupancy Vehicle (HOV) designation

The new reversible HOV/transit ramp at Mercer Street to the I-5 Express Lanes – scheduled to open to traffic after the completion of the Portage Bay Bridge and Roanoke Lid Project in 2031 – will have a HOV 3+ designation to match the HOV designation on SR 520, the highway it connects to.

Note: HOV designations are set by the state legislature and transportation commissions, not the Washington State Department of Transportation.

A commitment to equitable contracting

WSDOT is committed to providing equitable contracting opportunities to minority-owned, women-owned, veteran-owned and disadvantaged small businesses (MSVWBEs). Our goal is to provide 26 percent of our transportation projects’ contract value to these firms. See our equal opportunity in contracting webpage for more information and resources for working with WSDOT.

Construction on the SR 520/I-5 Express Lanes Connection Project is expected to last into spring 2024. The work includes building a new, elevated reversible HOV access ramp between SR 520 and the I-5 express lanes, constructing 23 retaining walls, and electrical and real-time traffic signage work. The prime contractor, Walsh Construction, has open contracting opportunities on the project for qualified MSVWBE firms for landscaping, hydroseeding, and Vactor truck operations. Subcontractors interested in working on this project should contact:

• Dylan Kennard, Assistant Project Manager, The Walsh Group, at dkennard@walshgroup.com
• Regina Glenn, WSDOT’s Megaprograms Diversity and Inclusion Manager, at GlennRe@consultant.wsdot.wa.gov