>>1903616Generally, a patch of unexpectedly light traffic. The schedule is built around a set of assumptions about how long loading takes, how often people are going to signal to exit, how much traffic is expected, how often that traffic is likely to need the kneeler, how often they need the bike rack, how often they need the wheelchair lift/secure area, and so on plus a little padding for if there's an unexpected problem that will delay the driver but won't required a replacement bus. If the route is surprisingly light one day, there are few or no special requirements passengers, and nothing unexpected happens all that "bonus" time gets dropped on the bus and that leg of the route finishes early.
Different bus systems handle this different ways. My local has chosen to treat the paper schedule as "set" times: if the schedule says they leave 7th and 12th at :55 past the hour, then they will not leave that location a moment before then. However, stops that either aren't on the schedule or don't have a fixed time next to them can be anywhere between the time before them or the time after them. So if there's a stop at 7th and 36th at :05 past the hour the stop at 7th and 24th with no number will be happening sometime between 5 till and 5 after, but no promises when. Any "extra" time gets eaten by the wait at 7/36 until its time to pull out.
Sounds awful. In practice, it works pretty well.
