> And if you improve public transit (I heard BART is some that's pretty good by American standards but not by European standards?)

BART is ~fine; there's just not very much of it. Only two lines go through San Francisco (both of which are essentially one line while _in_ San Francisco), plus there's one line worth of Caltrain (which is kinda low frequency; 3-4 an hour per direction peak time), and _that's about it_.