Technically, you're correct (train to SOMEWHERE every 6 minutes at peak periods in downtown SF-Oakland), but ... if you're trying to go to Fremont (not just Oakland) the trains do run about 20 minutes apart; there are just several going to other places in between. And remember when BART opened ... supposed to be a train every 90 seconds at rush hour? That never quite worked out, driverless or otherwise, even after the computer finally stopped forgetting where the trains were.

Was fun one morning coming in from Fremont. There had been some kind of hiccup, with a stalled train at Union City. So we left Fremont on the left track. There's a crossover north of Union City. When we got to Union City, the other train had been reactivated. Computer sent both of us out of the station at the same time, then both stopped, then one went forward & stopped, then the other, couple of times, until after an extended stop we went ahead and through the crossover to the normal track for the rest of the trip. Had the impression that somebody in Central Control finally had to manually tell the computer which one to pick.