George Cohen said Wednesday night that progress was being made.
The possibility of a strike has loomed each weekday since a 60-day cooling-off period expired last Thursday. But each time, BART and the unions have agreed to continue talking.
One factor in the negotiations has been safety. Wednesday, Amalgamated Transit Union Local 1555 President Antonette Bryant issued a challenge.
"Go check out the Daly City break room with mice running through it and walls that have urine running down them," she said. "Again, we are talking about issues that affect the health and wellbeing of our members."
When ABC7 News was shown the break room by a union member, there weren't any rodents, but it did smell of urine. Workers say transients urinate on the stairs and it runs inside.
But BART spokesperson Alicia Trost says the room is not the official break room for the Daly City station. The manager allows them to use the room because it's close to the gate. The official break room has showers, running water and meets all safety and sanitation standards.
BART workers walked off the job for nearly five days in July. That strike resulted in traffic jams and long lines for buses.
BART is the nation's fifth-largest rail system. It serves about 400,000 riders each weekday.
The Associated Press contributed to this report.
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