The Bay Bridge is back open, providing relief to drivers who stayed in town over the Presidents Day weekend and were caught up in the gridlock during the closure.

The bridge's upper deck reopened Sunday evening, nearly a day and a half ahead of schedule. Caltrans spokesman Bart Ney said unexpectedly good weather allowed work to progress quickly.

The closure allowed crews to construct a detour for westbound cars that will allow for the construction of part of the new eastern span.

Motorists passing through the toll plaza are asked to drive carefully on the new detour, since the merge is different. While 20 lanes still merge down to five, they curve slightly to the south, Ney said.

During the closure, which began at 8 p.m. Friday, motorists trying to get from the East Bay to San Francisco had to take alternate routes, and traffic slowed to a crawl on the Bay Area's other bridges.

On Saturday, more than 67,600 southbound vehicles crossed the Golden Gate Bridge, compared to 39,799 on the Saturday of Presidents Day weekend last year, bridge district officials said.

BART tallied 236,600 riders on Saturday -- the fifth-highest Saturday ridership in the agency's history. The highest Saturday ridership was 278,600 riders on Sept. 1, 2007, when the bridge was shut down and three major sporting events were scheduled.

Ney said Bay Area residents won't have to worry about another bridge closure for a while.

"The next time we plan to close the Bay Bridge will be to open the new Bay Bridge, Labor Day weekend 2013," Ney said.