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

Work starting soon on a reversible bus/carpool lane between SR 520 and South Lake Union

Construction should begin later this summer 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

Crews work from an over-water platform to construct concrete columns that will support a new eastbound SR 520 bridge over Union Bay in Seattle.  Two rows of columns extend into the distance, with traffic flowing to their right  on the westbound bridge.

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 replacement, as shown in this late-June photo. The two rows of fluted concrete columns rising from the water will 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 right) will revert back to a westbound-only bridge. You can view more SR 520 photos in our Flickr collection.

Progress continues on new freeway lid over SR 520 in Seattle

Aerial view of construction on a future freeway lid over SR 520 in Seattle, showing sections of exposed support beams, plywood formwork, rebar, and concrete decking.

Our contractor crews are making steady progress constructing a new freeway lid over SR 520 in Seattle's Montlake neighborhood. In this May photo, looking west toward Portage Bay, the white section at the top, near Montlake Boulevard, is new concrete decking. The greenish section just below it is installed rebar, awaiting the next concrete pour. The tan-colored section below the rebar is plywood formwork. And finally, just west of 24th Avenue East, are exposed concrete beams, called girders, that support the lid's weight. Later this year, crews will shift Montlake Boulevard and 24th Avenue East onto the lid, remove the two old overpasses, extend the lid both east and west, and then build new, improved street crossings over the highway. 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