The state Department of Transportation just announced that the Alaskan Way Viaduct will reopen by midday Saturday, because demolition has gone well all week.

The state Department of Transportation just announced that the Alaskan Way Viaduct will reopen by midday Saturday, because demolition has gone well all week.

The northbound lanes already are open from Royal Brougham Way to the Battery Street Tunnel and South Lake Union. The rest of the highway had been scheduled to reopen Monday morning, with a detour route where the southern end of the viaduct used to be.

Commuters this week have endured occasional periods of “Viadoom,” where the loss of about 90,000 vehicles worth of daily highway capacity led to traffic jams. The worst occurred Thursday afternoon, when diverting drivers and stalls on other highways caused congestion as far out as Shoreline and Bothell. But overall, driving declined by perhaps 20 percent, analysts said.

Starting Saturday, drivers will go through the Sodo section of Highway 99, where four lanes of traffic will squeeze onto a new Viaduct overpass at the train tracks. Then the detour curves through a 25 mph zone. The speed limit for the entire Viaduct, including the waterfront, has been reduced to 40 mph. The detour will remain in effect until the start of 2016, when the state is scheduled to open a downtown bypass and stadium interchange, altogether a $3.2 billion replacement for the 1950’s vintage elevated highway.

The demolition, by Skanska USA and Rhine Demolition, reduced more than 2,800 feet of highway to rubble. “Thank you to the hard workers on this project, and the people of the region who were patient, found alternate routes and adjusted their schedules. Everyone showed a great spirit of cooperation,” said Gov. Chris Gregoire in a statement.

King County Metro said its buses will return to normal routes on Highway 99 and in Sodo, starting Sunday. The Seahawks play a home game Sunday at 1:15 p.m.