SR 520 - West Approach Bridge North Project - Completed December 2017


The West Approach Bridge North is the most recently completed segment of the SR 520 Bridge Replacement and HOV Program. Opened to traffic in summer 2017, the new approach bridge extended SR 520’s three westbound lanes and the SR 520 Trail from the new floating bridge to the Montlake area in Seattle. We are building a parallel West Approach Bridge South, for eastbound traffic, as part of the SR 520 Montlake Project. To enable the removal of the old, structurally vulnerable west approach bridge and make room for constructing the West Approach Bridge South, we've temporarily shifted all traffic over Union Bay onto the north bridge,  with two lanes in both directions. 

Project timeline

  • September 2014: Began construction
  • July 2017: Opened new westbound off-ramps to Montlake area
  • August 2017: Opened new bridge to traffic
  • December 2017: Opened SR 520 Trail between Montlake and new floating bridge

Project Benefits

Improves safety

  • The old 1963-era west approach bridge is a fixed structure supported by hollow columns, and is vulnerable to a catastrophic earthquake. The new West Approach Bridge North, built to current earthquake standards, is designed to withstand a magnitude of earthquake that’s expected to happen only once in 1,000 years.
  • For the next three to four years while we remove the old west approach bridge and construct a three-lane structure for eastbound travel, both eastbound and westbound traffic will travel between Montlake and the floating bridge on the West Approach Bridge North, with two general-purpose lanes in each direction, and no transit/HOV lanes.

Relieves congestion

  • The new West Approach Bridge North extended SR 520’s three westbound lanes (including an HOV/transit lane) to Montlake. The bridge also includes a wide shoulder that allows vehicles to pull over, without blocking traffic, in case of a breakdown.

Provides multimodal options

  • The new approach bridge extends the 14-foot-wide SR 520 bicycle and pedestrian trail across Lake Washington, providing a new cross-lake connection.
  • The addition of transit/HOV lanes and a cross-lake shared-use trail provide greater reliability and more travel options to accommodate growth in the region.

Protects environment

  • The new approach bridge expands access and facilities for public transportation and nonmotorized transportation options with low carbon emissions.
  • The project removed from the Washington Park Arboretum the old westbound off-ramp and unused R.H. Thomson “Ramps to Nowhere” – part of WSDOT’s commitment to help restore the Arboretum.
  • The SR 520 Program has also participated in numerous mitigation projects to protect the natural environment of the greater Lake Washington watershed. Learn more about these projects and other environmental benefits on our SR 520 - Environmental Stewardship page.

Financial Information

The project was funded by a variety of state and federal sources. The final cost of the West Approach Bridge North Project was approximately $210 million.
Visit the SR 520 Budget and Performance page for additional information about SR 520 program funding.

Partnerships and cooperation

WSDOT and its contractors worked closely with local, state and federal officials, Native American tribes, regulatory agencies, environmental groups, community organizations, transit agencies and many others during the planning, design and construction of the new West Approach Bridge North. These partnerships helped inform a number of construction documents, including the Neighborhood Traffic Management Plan (pdf, 1.37 mb) and the Seattle Community Design Process Final Report (pdf, 21.9 mb).

How can I get more information?

Info line: 206-770-3554
Twitter: @WSDOT_520

SR 520 Bridge Replacement and HOV Program
999 Third Ave., Suite 2200
Seattle, WA 98104

Location map of West Approach Bridge North project
View larger map

Hollow columns on the existing west approach bridge
2006 photo of a damaged hollow column on the existing west approach bridge that has since been repaired. The columns for the West Approach Bridge North Project are built to modern earthquake standards.