Key issues in the labor dispute include salaries, pensions, health care and safety.
BART has said workers from the two unions 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.
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.