Don't forget that rail (usually) has its own right-of-way.A badly planned bus system is never faster than driving; you're stuck in the exact same traffic. Rail (especially subway or Rapid Transit) though, automatically has the benefits of BRT... it doesn't get stuck in traffic.
Also when looking at e.g. Light Rail that goes on the road (like Muni's LRVs) you should consider the socioeconomic factors - the bus is looked down as for poor people in a way rail transit isn'. (Which is why, for instance, the NX is a thing; people wanted and got a specially painted bus while the N was undergoing renovations so they wouldn't be on the "common people" bus.)
Remember - a "regular" bus is never faster than driving.
Also when looking at e.g. Light Rail that goes on the road (like Muni's LRVs) you should consider the socioeconomic factors - the bus is looked down as for poor people in a way rail transit isn'. (Which is why, for instance, the NX is a thing; people wanted and got a specially painted bus while the N was undergoing renovations so they wouldn't be on the "common people" bus.)
Remember - a "regular" bus is never faster than driving.