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 mass transit, and give the public new and better options for nonmotorized travel.
Program construction, which began in 2011, is being done in phases under separate projects and contracts. Click on the links below to visit our individual project pages and learn more about the reconstruction of SR 520.
The 2015 Legislature authorized funding to complete the design and construction of SR 520’s west side improvements in Seattle. These include a new Portage Bay Bridge, a new west approach bridge for eastbound traffic, new highway lids in the Montlake and Roanoke neighborhoods, and extension of a new regional bicycle and pedestrian path from Montlake to I-5.
SR 520's existing, four-lane west approach bridge, which links Seattle to the old floating bridge, is supported by hollow columns that could fail in a strong earthquake. We are replacing it with a new west approach that meets current seismic standards. Now under construction is the new approach's north half, which will carry westbound traffic from the new floating bridge to Seattle. The south half, not yet under construction, will ultimately carry eastbound traffic from Seattle to the new floating bridge.
Floating Bridge and Landings Project
We 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, which opened April 2016, also has shoulders for disabled vehicles and a separate, 14-foot-wide path for bicyclists, walkers and joggers.
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 the first completed segment of a new, regional cross-lake bicycle and pedestrian path and three community-connecting highway lids.
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.