Bay Area transit officials warned commuters late Wednesday to make alternate transit plans on the July Fourth holiday as rail workers are expected to continue their strike.
BART said there was no indication that its two largest labor unions would return to work Thursday.
Negotiators and both sides were still working late into the evening Wednesday after beginning talks about 1 p.m.
Key issues involve salaries, pensions, health care and safety.
The strike is in its third day. Heavy morning rush-hour traffic lightened considerably by midday as the holiday approached.
Josie Mooney, a chief negotiator with Service Employees International Union Local 1021, said she was hopeful the latest round of talks could end the three-day strike that has slowed commutes across the San Francisco Bay Area.
Mooney appeared optimistic after an overnight bargaining session Tuesday that lasted nearly nine hours.
"We made some progress. We've worked very hard," Mooney said. She declined further comment, saying a mediator had asked the parties not to speak to the media.
Key issues in the labor dispute involving the nation's fifth-largest rail system include salaries, pensions, health care and safety.
BART spokesman Rick Rice said the long meeting was a good sign.
"It's a lot better than not talking," he said.
The strike, however, continues to cause stress and frustration in the region. Commuters lined up early Wednesday for the transit agency's charter buses at five locations, waited patiently for ferries heading to San Francisco, and endured heavy rush-hour traffic on the San Francisco-Oakland Bay Bridge that lightened considerably by midmorning.
"I hope this is the last day," Teresa Hardin, 52, of Oakland, a benefits consultant, said before she boarded a San Francisco-bound ferry. "It's becoming harder to be sympathetic to either of the parties right now."
BART serves more than 400,000 commuters each weekday. The strike began early Monday after talks broke off. Negotiations resumed Tuesday as political pressure and public pleas mounted.
The Governor's Office sent two of the state's top mediators the chair of the Public Employment Relations Board and the chief of the State Mediation and Conciliation Service to facilitate further talks.
A letter from the state controller, lieutenant governor and insurance commissioner said the strike has caused "widespread personal hardship and severe economic disruption," and it noted they were disappointed "about the lack of productive proposals and counterproposals in the days leading up to the strike."
BART has said union train operators and station agents average about $71,000 in base salary and $11,000 in overtime annually. The workers also pay a flat $92 monthly fee for health insurance.
Commuter Hilary Hartman, 26, said she has a hard time sympathizing with the unions' demands for more money.
"They make almost twice as much as I do," Hartman said while waiting on Tuesday to take a bus from San Francisco to her job in Berkeley. "I work for a nonprofit. If I don't do my job, I get fired. I'm kind of like, please come do your job so I can do my job."
Despite such feelings, no backlash is likely against the union, said Steven Pitts, a labor policy specialist at UC Berkeley's Center for Labor Research and Education.
Even though only about 11 percent of workers in the nation are union members, California is one of the more heavily unionized states in the country, he said, with San Francisco and Los Angeles serving as union strongholds.
"In this case, BART's unions feel that they have some leverage due to the lack of similar transit alternatives in the area, and BART can't run the trains without its workers," Pitts said.
BART travels through the farthest reaches of San Francisco's densely populated eastern suburbs to San Francisco International Airport across the Bay. With 44 stations in four counties and 104 miles of lines, the trains handle more than 40 percent of commuters coming from the East Bay to San Francisco, area transportation officials said.
To aid commuters, BART has extended the hours of carpool lanes and added ferries and buses.
The unions which represent nearly 2,400 train operators, station agents, mechanics, maintenance workers and professional staff want a 5 percent raise each year over the next three years.
BART said it is offering an 8 percent salary increase over the next four years as well as reducing the amount of employee contributions it originally requested for pension and medical benefits.