The process is fairly simple: carpoolers wait in the morning at one of the casual carpool stops in the East Bay between 6 a.m. and 9:30 a.m. The stops are usually marked by signs. Drivers pick up passengers on a first come, first served basis.
Drivers have to subscribe to FasTrak and need to pick up at least two riders to go on the HOV carpool lanes on the Bay Bridge.
The passengers are dropped off on Fremont Street in downtown San Francisco.
Antoine Justin has been commuting this way from Vallejo to San Francisco for years. He says there is an etiquette for casual carpooling.
"Of course be courteous, be polite, don't talk too much on the phone; just to be respectful, not rude," Justin said.
There are dozens of pickup stops to choose from in the East Bay, most of them in Oakland.
If there is a BART strike Monday morning, Bay Area transportation officials are encouraging commuters to try casual carpooling. In fact, they want BART to help make that happen.
"It would make perfect sense that the BART stations, in the event of a strike, that their parking lots would be available as Park and Ride locations," Metropolitan Transportation Commission spokesperson John Goodwin said.
There will be extra bus and ferry service, but that will only help accommodate a small part of BART's 400,000 daily riders.
"That's really the only way to capacity that's lost in a BART strike could be made up," Goodwin said. "It's the empty seats in people's cars."
Casual carpool driver John Diamond is doing his part. He always carries a full car with three riders. But come if there's a strike?
"Well, it's one of those things where it might be better for me to stay home," he said.
So will many passengers.
"If it does, management is thinking about telecommuting for the employees, so that'll be an option," casual carpool passenger Abhay Prasad said.
"Well, I'm going to take vacation; I'll just stay home then," casual carpool passenger Maria Ortega said.
Others said they'll just wait to see what happens before making plans.