How a small delay becomes a bigger one
A bus that falls behind schedule does not simply lose time on the road. It may also meet more waiting passengers at each stop. Those extra boardings keep its doors open longer, adding delay; the longer it runs late, the more passengers may accumulate at later stops.
Meanwhile, the bus behind it encounters fewer people, because some riders who would have taken that bus are already aboard the delayed one. It can make shorter stops and close the gap. This feedback loop is called bus bunching: a modest disruption can turn two evenly spaced buses into a pair traveling almost together, followed by a longer-than-usual wait.
Why the timetable cannot prevent it by itself
A timetable lays out when a bus is expected to pass particular points, but traffic, signals, boarding time, and other delays vary from trip to trip. If a schedule has little recovery time built in, a late bus may have no chance to regain its spacing before the next busy stop. The published times are therefore most useful as a plan for service, not a promise that every arrival will happen to the minute.
Transit agencies can manage the spacing as well as the clock. Depending on the route and operating conditions, dispatchers may ask a bus to wait briefly, move faster, or turn around early so that service is spread more evenly. These choices can make one bus depart later than its timetable suggests, but reduce the chance that riders face a long gap followed by two buses at once.
The useful measure is often the gap
For riders, the distance in time between buses can matter more than whether each bus matches its printed time. When a bus is delayed, checking live arrival information—or allowing extra time on a crowded or traffic-prone route—can help. The key problem is not just lateness: it is how one late bus changes the spacing of every bus behind it.
