Crews have started work on the new detour, alongside the existing westbound deck. But with the detour, drivers will experience a slight alignment change as traffic is shifted to the south away from the construction.
"Four days, basically, to push traffic onto it," San Francisco-Oakland Bay Bridge spokesperson Bart Ney said. "We're finishing the heavy construction right now, motorists can see it. The widening that we had to do to the incline is nearly done. By Presidents' Day weekend all of the paving and all the intermediate space will be complete."
Only one thing could delay the reopening of the bridge.
"The challenge for this particular closure is weather, because we can't stripe and put all the patterns in if it's raining," Ney said.
During Presidents Day weekend, the bridge will still be open for people driving to the East Bay.
For those trying to get to San Francisco, BART will have overnight service. Buses will still be operating, dropping commuters off at BART stations.
"We will be running transbay bus services, only it won't be crossing the bridge, per say. Our buses will terminate at the West Oakland Bart station," AC Transit spokesperson Clarence Johnson said.
By putting in that detour now, the entire bridge will open ahead of schedule.
"Our previous schedule had us literally opening westbound traffic into San Francisco in late 2013, and then keeping the eastbound traffic on the old bridge for another six months to a year to do the work we are going to do now," Ney said.
All the previous closures have happened over Labor Day weekend but Caltrans says it can't wait until then.