Highway 520 will close to travelers in both directions across Lake Washington this weekend while crews shift lanes to make room to construct structural supports for a planned lid over the highway at Montlake.

The bicycle and pedestrian trail will stay open but all vehicular traffic, including bus routes, must detour.

Drivers needing to cross the lake should take alternate routes. The Washington State Department of Transportation (WSDOT) advised travelers to use Highway 522 or Interstate 90 — or stay home.

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About 160,000 vehicles travel across the lake between Seattle and the Eastside on an average weekend, WSDOT says.

The roadway will close at 11 p.m. Friday and reopen at 5 a.m. Monday.

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Both directions of Highway 520 will be closed between Montlake Boulevard and 92nd Avenue on the Eastside. All on- and offramps within that stretch also will be closed.

In addition, westbound lanes between Montlake and Interstate 5 will be closed. Highway 520 eastbound will remain open between I-5 and Montlake Boulevard, but drivers must exit at Montlake.

This weekend’s work is part of WSDOT’s $455 million project to construct new eastbound lanes between Montlake Boulevard and the floating bridge, build a lid over the highway and make changes to the Montlake Boulevard interchange, among other projects.

Crews have shifted traffic to different lanes on other weekends to build the center structural support structure for the lid, which will include a transit hub.

Travelers should expect another weekend of closures Sept. 12 and 13. With no University of Washington football, the impact on traffic should be less, said WSDOT spokesperson Steve Peer.