SR 520 Bridge Replacement and HOV Program major projects

The SR 520 Bridge Replacement and HOV Program is rebuilding one of the Puget Sound region's busiest highway corridors to improve traffic safety, enhance regional mobility, and give the public new and better options for nonmotorized travel.

Since construction began in 2011, we've rebuilt the highway's Eastside segment between I-405 and Lake Washington, replaced the old floating bridge with a new, six-lane span, and completed the first of two parallel west approach bridges over Union Bay. We'll complete all remaining SR 520 construction in coming years with four additional projects, which we collectively call the "Rest of the West." These remaining projects are the Montlake Project, the SR 520/I-5 Express Lanes Connection Project, the Montlake Cut Bascule Bridge Project, and the Portage Bay Bridge and Roanoke Lid Project.

Our individual project web pages provide more information about SR 520's reconstruction. Below are snapshots of the next projects we'll undertake and the SR 520 projects we've already completed.

Montlake Project

conceptual rendering of a new Montlake lid transit centerThe Montlake Project kicked off our remaining SR 520 improvements between Lake Washington and I-5. The project includes construction of an improved Montlake Boulevard interchange, a landscaped lid over SR 520, a bicycle/pedestrian "land bridge" east of the lid, and a three-lane West Approach Bridge South, over Union Bay, for eastbound traffic. Major construction of the Montlake Project began in summer 2019.

I-5 Express Lanes Connection Project

A snap shot from a video showing the state route 520 and interstate 5 interchange with a new ramp connection highlighted in purple.

It's no secret that the Puget Sound area is experiencing a population and employment boom. The region's growth underscores the importance of a safe, reliable transit/HOV link between Seattle and the Eastside via SR 520. This project will extend SR 520's new transit/HOV system onto the I-5 express lanes, creating a direct bus and carpool connection between SR 520, South Lake Union and downtown Seattle.

Montlake Cut Bascule Bridge Project

A bridge crosses the Montlake Cut.

Montlake Boulevard East (SR 513) is one of the busiest arterial corridors in the city of Seattle, linking northeast Seattle and the University District with SR 520 and north Capitol Hill. The SR 520 reconstruction program includes legislative funding for a second, parallel drawbridge over the Montlake Cut. WSDOT plans to bring together project partners, stakeholders, and the public to review current transportation needs, identify potential options for improving mobility in the Montlake Boulevard and SR 520 corridors, and discuss this project's scope.

Portage Bay Bridge and Roanoke Lid Project

A rendering of the future Portage Bay Bridge.The 1960s-era Portage Bay Bridge is nearing the end of its functional life. Supported by hollow concrete columns, the four-lane bridge could fail in a severe earthquake. This project will replace the old bridge with a seismically stronger structure. The project also will build a landscaped lid over the highway in Seattle's Roanoke neighborhood, and extend SR 520's transit/HOV system and cross-lake bicycle and pedestrian trail from Montlake to I-5.

West Approach Bridge North Project (completed)

photo of new West Approach Bridge North over Union Bay in Seattle

SR 520's old, four-lane west approach bridge is supported by hollow columns that could fail in a strong earthquake. We are replacing the structure with two parallel, three-lane bridges that meet current seismic standards. We opened the new approach's north half in August 2017 to carry three lanes of westbound traffic from the new floating bridge to Seattle. (This bridge currently carries two lanes of traffic in both directions while we remove the old west approach bridge and build an eastbound West Approach Bridge South.)

Floating Bridge and Landings Project (completed)

photo of the new SR 520 floating bridge on Lake WashingtonWe replaced the world's longest floating bridge - a four-lane structure built more than a half century ago - with an even longer, safer, six-lane bridge designed to withstand strong windstorms and waves. The new bridge, opened in April 2016, also has shoulders for disabled vehicles and a separate, 14-foot-wide path for bicyclists, walkers and joggers.

Eastside Transit and HOV Project (completed)

photo of riders boarding a bus at the Evergreen Point Road transit station New HOV lanes, median transit stops, and direct-access ramps for buses and carpools are among the many improvements we've completed on SR 520's Eastside corridor. This 2.3-mile stretch of rebuilt highway also features three community-connecting highway lids and the first completed segment of a new, regional cross-lake bicycle and pedestrian path.

Pontoon Construction Project (completed)

photo of the WSDOT pontoon casting basin in Aberdeen, Washington This project built 33 of the new floating bridge's 77 pontoons at a casting basin in Aberdeen, Wash. The final three Aberdeen-built pontoons were completed in March 2015. The 44 other pontoons needed to support the new bridge were built at a casting basin in Tacoma. Construction there wrapped up in late 2014.