i'm not sure i get your question about the bus – you have to take a bus either way, the question is what kind of bus.
if you're boarding at the colliseum, then you take the AirBart shuttle to get to the BART station, then you use the pedestrian bridge to cross the street to get to the amtrak stop.
i'm not sure how the bus to emeryville works. are you talking about the amtrak thruway coach?
i think that in terms of being on time, it really doesn't matter that much. the segment between emeryville and oakland should not be subject to freight delays, i think.
ok to be honest i've never taken the train south of richmond, so i don't know much
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