The upper deck of the Bay Bridge will be closed next month over the Presidents Day weekend, but the shutdown of all westbound lanes on the nation's third-busiest bridge could be a time saver in the long run.

Caltrans said the closing, for three or more days, could shave six months off the projected 2014 opening of the eastbound lanes. That means the most expensive public works project in state history, at $6.3 billion, could be done by the end of 2013.

For the 280,000 daily motorists who have put up with the bridge's twisting lanes and distracting construction since work began in 2002, that is welcome news.

"Caltrans has done a pretty good job, but the Bay Bridge is the Bay Bridge and traffic is never pleasant through there, especially where the lanes curve and drivers go far too fast," said Maria Filios, of Fairfield, who commutes to San Francisco. "Getting done early will be nice."

Crews will use the closing to work between the existing and new bridges to complete the new eastbound lanes, which Caltrans says is not possible without the traffic realignment. The westbound lanes are in the path of the new bridge's eastbound lanes.

Without the detours, eastbound traffic would have stayed on the original bridge for about six months after westbound traffic traveled on the new bridge.

The detour will be installed near the toll plaza, and drivers will find a slightly different approach to the bridge after the work.

The timing is a gamble. Caltrans has closed the bridge several times, but only over the Labor Day weekend, when traffic is the lightest of any holiday and when it seldom rains. This time, rain and high winds could threaten the work.

"Our real challenge this time is weather," Caltrans spokesman Bart Ney said. "We'll be watching it very closely. It's possible this could be delayed."

Contact Gary Richards at 408-920-5335.

CLOSING WESTBOUND LANES ON BAY BRIDGE
When: From 8 p.m. Feb. 17 to 5 a.m. Feb. 21
Options: Additional ferries, overnight BART service at certain stations and AC Transit will be provided; check 511.org for transportation alternatives
Cost: $6.3 billion
Projected completion: Late 2013
Details: www.baybridgeinfo.org