Interstate 405 will be closed — in both directions — between Northeast Eighth Street and State Route 520 this weekend.

Construction crews will be removing the old Northeast 12th Street Bridge and must close the freeway because they cannot safely take down the bridge while traffic passes under it.

The closure will impact nearly 450,000 vehicles, the number that uses this portion of I-405 on a given weekend. The closure is Washington State Department of Transportation’s biggest this construction season.

Removing the bridge will allow crews to finish building a new, longer, wider bridge over I-405 at Northeast 12th Street. The state is replacing the bridge to make room for new northbound ramps from Northeast Eighth and Northeast 10th streets. The project is designed to improve safety and traffic flow between I-405 and SR 520.

Crews will close I-405 in both directions from tonight at 11 p.m. to Monday at 4 a.m. Crews will also close Northeast 12th Street from 112th Avenue Northeast to 116th Avenue Northeast and many area ramps during the same weekend.

Motorists are urged to use alternate routes or defer trips during the 53-hour closure period as the state anticipates congestion throughout the region. Northbound I-405 off-ramps will be open as far as Northeast Eighth Street. Southbound drivers will detour via SR 520 to 108th Avenue Northeast.

The state recommends motorists use recommended regional routes unless they plan to visit Bellevue. Downtown Bellevue will be open for business. Drivers should expect heavy traffic on the detour routes and throughout the region.