It's a completely separate system running diesel trains on an entirely different rail gauge [0]. It also tends to be inaccessible a lot because BART can't keep

It's a completely separate system running diesel trains on an entirely different rail gauge [0]. It also tends to be inaccessible a lot because BART can't keep the lines running, so getting to SF or Oakland often involves a bus transfer on top. [0] https://en.wikipedia.org/wiki/EBART https://en.wikipedia.org/wiki/EBART