BART was intended to go there when they first started building it, iirc. Marin dropped out of BART, and then San Mateo county. This is why there's the double d

BART was intended to go there when they first started building it, iirc. Marin dropped out of BART, and then San Mateo county. This is why there's the double decker tunnels downtown - one was intended to branch off towards Marin.