Contracts between BART and its five unions expire on Sunday, and negotiations are at a standstill.
State mediators have been called in, and BART's two largest unions are conducting a strike authorization vote among their members today.
The two unions are Amalgamated Transit Union Local 1555, which represents 945 station agents, train operators and foreworkers, and Service Employees International Union Local 1221, which represents 1,430 mechanics, custodians and clerical workers.
Antonette Bryant, a spokeswoman for ATU Local 1555, said a joint statement will be released Wednesday morning detailing the results of the strike vote.
"We are fighting to get a contract," Bryant said.
She said, however, that the union hopes to avoid a strike.
BART spokeswoman Alicia Trost said the agency is also trying to prevent a strike from happening. She said the unions' decision to hold a strike authorization vote today has delayed negotiations until Wednesday.
"We think there is a deal to be had," she said.
The Metropolitan Transportation Commission is working on putting together a contingency plan in case a strike occurs.
Trost said BART is "not at the point of warning our passengers."
The MTC has posted an alert on its 511.org website that warns of a possible BART strike as soon as Monday.
The agency is advising commuters to plan ahead and try to work from home or carpool. Heavy traffic and overcrowded public transit systems are likely in the event of a strike, MTC officials said.
MTC spokesman John Goodwin said additional service will be used if a strike occurs, such as extra San Francisco Municipal Railway buses and light-rail vehicles and ferry service.
As to a possible strike, Goodwin said, "this will definitely create a pinch" for commuters in the East Bay, San Francisco and the northern peninsula.
He said employers and employees need to talk about travel plans and commuters need to arm themselves with information and back-up plans if there is no BART service.
"If there is a BART strike, travel around the region...is going to be impacted," Goodwin said. "In some cases it may be severe."
Muni spokesman Paul Rose said the transit agency is working with the regional transit authorities to develop contingency plans that prioritizes service along popular routes such as the Metro lines N-Judah and J-Church, along with the 49-Van Ness and 14-Mission bus line.
Fare inspectors will be out in full force to assist customers unfamiliar with Muni service, while parking and traffic staff will be helping to mitigate congested roads.
Rose suggested using casual carpooling, and said that the taxi industry is being told to make themselves available at busy points in the city.
At a union news conference in San Francisco this morning, SEIU Local 1021 spokeswoman Leah Berlanga pointed to a lawsuit filed by the two unions in Alameda County Superior Court on Monday morning in which they allege that BART is failing to bargain in good faith over worker safety.
"BART has not addressed safety issues and proposals we put on the table," Berlanga said.
Among other measures, the unions are demanding improved lighting on the tracks and in the stations.
San Francisco Supervisor David Campos said he stands in solidarity with the workers, and highlighted the importance of safety. He underscored the case of BART electrician Robert Rhodes, who was killed while working on the 24th Street station tracks in 2001.
"It's only appropriate that we ensure their safety on a daily basis," he said.
Campos called for "reasonable, open, good-faith negotiations." The supervisor said he doesn't want a strike, but that the safety issues need to be resolved before the unions can agree on a contract.
Trost has previously said that union leaders haven't mentioned safety issues in their own internal communications about the labor talks, instead emphasizing matters such as salaries, benefits and work rules.