The SR 520 corridor is a critical regional highway that is being rebuilt to support many modes of travel. The improved corridor in Seattle will:
Below are the four main stages of SR 520 construction ahead between Lake Washington and I-5 - the Rest of the West:
Montlake Project
Key elements:
Timeline: construction planned to begin in early 2019; estimated duration: 4-5 years
SR 520 / I-5 Express Lanes Connection Project
Key elements:
Timeline: construction planned to begin in 2020; estimated duration: 3 years
Montlake Cut Bascule Bridge Project
Key elements:
Timeline: WSDOT will conduct additional coordination with community stakeholders and agency partners regarding the scope of the Montlake Cut Bascule Bridge Project.
Portage Bay Bridge and Roanoke Lid Project
Key elements:
Timeline: construction planned to begin in 2023; estimated duration: 6 years
Additional design resources:
Public engagement
WSDOT has worked since the late 1990s with the city of Seattle, agency partners, stakeholders and the public to develop, analyze and refine SR 520 designs and solutions.
In 2006, the draft environmental impact statement considered three choices for the project: a four-lane highway, a six-lane highway, and a not-building-anything option. Analysis and public feedback led WSDOT to drop the four-lane alternative and study further the no-build and six-lane alternatives. In 2010, following additional public review and feedback, a six-lane "Preferred Alternative" design was endorsed.
The Preferred Alternative went through more rounds of analysis and refinement, most notably the Seattle Community Design Process in 2011-2012. This robust and collaborative effort between WSDOT, the city of Seattle, design professionals, and the broader public resulted in a refined corridor vision and conceptual design.
From 2014 through 2016, a team of design professionals, working in collaboration with the Seattle Design Commission and supported by WSDOT and city staff, recommended design refinements. Check out our final concept design report for more details.
Visit our Montlake Project page to learn about ways to stay engaged as we prepare for construction.