SEATTLE – Seattle’s Alaskan Way Viaduct is set to close for two weeks starting Friday and transportation officials are urging commuters to plan ahead.

The closure is expected to cause widespread traffic throughout the region.

The Washington state Department of Transportation will close State Route 99 between South Spokane Street and the south end of the Battery Street Tunnel.

The agency says the closure is need because the tunneling machine known as Bertha will begin digging underneath the roadway near Yesler Way.

The agency is encouraging commuters to work from home, adjust work schedules or try alternatives such as taking bus, light rail, water taxi or vanpools.