SR 520 Bridge Replacement and HOV Program


For the most up-to-date information about SR 520 construction activities and planned road closures, visit and bookmark our SR 520 Construction Corner and its interactive construction map. You also can view Montlake Project construction photos taken daily, 'round the clock, by four mounted construction cameras.

Current News

Construction begins on a reversible bus/carpool lane between SR 520 and South Lake Union

Construction is now underway on a reversible bus and carpool connection between SR 520 and I-5's Mercer Street interchange. The SR 520/I-5 Express Lanes Connection Project will provide faster, more reliable bus and carpool travel between the Eastside and Seattle's bustling South Lake Union neighborhood. This blog article and video provide more information on this project. 

Moving forward on a new eastbound bridge over Union Bay

Gray concrete columns rise out our Union Bay where crews are constructing a new eastbound SR 520 bridge over Union Bay in Seattle. To the left of the bridge under construction is the completed West Approach Bridge North, with traffic flowing on it.

With the old, 1960s-era SR 520 west approach bridge over Union Bay now largely removed, our Montlake Project crews are focused on building its eastbound replacement, as shown in this mid-October photo. The two rows of fluted concrete columns rising from the water will help support a seismically resilient, three-lane bridge for eastbound traffic. The 1.2-mile-long bridge will carry traffic from Montlake to the SR 520 floating bridge. Once crews complete the new eastbound bridge, they will remove the temporary work platforms flanking both sides of the columns. After the new bridge opens, expected in 2023, the north span (at left) will revert back to a westbound-only bridge. You can view more SR 520 photos in our Flickr collection.

Montlake Boulevard takes a new path

Aerial photo showing Montlake Boulevard before and after traffic lanes were shifted onto a freeway lid over SR 520 that is under construction.

Montlake Boulevard no longer follows a fairly straight line across SR 520, as was the case in the July photo at left. Instead, the busy arterial now curves over the highway (in photo at right) atop the center section of a new freeway lid that's under construction in Montlake. The shifted lanes will allow crews to remove the old overpass, extend the lid westward, and build a new, improved Montlake Boulevard crossing over the highway. A similar process will begin soon with the 24th Avenue East overpass at the east end of the Montlake lid. When completed, the three-acre lid will feature a regional transit hub, landscaped open space, and bike-pedestrian connections. Our crews expect to complete the SR 520 Montlake Project in 2023.

Program overview

The SR 520 Bridge Replacement and HOV Program is enhancing public safety and mobility by replacing the highway's aging, vulnerable bridges and making significant transit and roadway improvements throughout the corridor. Built in stages, the construction program's completed and planned improvements extend from I-405 in Bellevue to I-5 in Seattle.

map of the SR 520 corridor's major projects

Click on the map above to visit our SR 520 Major Projects webpage.


Phone: 206-770-3500
Find SR 520 Program contact information: Contact Us