Not necessarily. If the full bus stays in front, then there will be lots of people waiting at every future stop, trying to get on the full bus, taking ages to d

Not necessarily. If the full bus stays in front, then there will be lots of people waiting at every future stop, trying to get on the full bus, taking ages to do so. If the full bus lets the empty bus pass, then all the people waiting at the next stop can get into the empty bus. When the full bus arrives at the next stop, right behind the formerly empty bus, nobody needs to get on, only people need to get off, so they don't need to stop as long at the next stop.