It is hard for buses to keep a schedule or target headway because traffic, riders, drivers, and weather are unpredictable and can vary greatly over the day. This variability creates a tendency for buses to bunch. Here is how it works: Suppose the buses on a route are perfectly-spaced, at equal time intervals so no one has to wait long for a bus. When, by chance, one bus is delayed, perhaps at a traffic light, there will be a larger gap (headway) in front of it and this bus will encounter more passengers to load at each stop, and so fall still further behind. The following bus will have a shorter headway, see fewer passengers, and so gain still more on the leading bus.
Things only get worse: Large headways tend to grow and small headways tend to shrink, and ever more strongly. The result is that many passengers must wait for a long time and then two or more buses arrive together, with the first one full and the trailing bus nearly empty. Indeed, bunching is the most frequent complaint about any urban bus system, as a web search on “bus bunching” will confirm.
Bunching is not only bad service, it is bad economics because any bus with a short headway is being underutilized, and driver-time wasted.
Abandon the schedule!
No one cares about a schedule as long as the gaps between buses (the headways) are small. A target schedule or headway is just an aspiration. It never survives contact with the real world. Instead, work to equalize headways by strategically pausing buses briefly at certain designated stops (“layover points”), such as the ends of the route or at transfer points, or anywhere the bus can pull out of traffic briefly. By this means BusGenius coördinates the buses on a route to keep them arriving at regular, short intervals, and with no schedule, no dispatcher, no intervention by management — even without intention or awareness of the drivers.
BusGenius watches and learns your route. It recognizes when a bus arrives at a layover point, and, based on where all the other buses are and recent travel times, BusGenius will adjust headways to become more nearly equal — and without anyone having to guess in advance what headways “should be”. BusGenius establishes the shortest headway possible under current conditions to ensure that no one has to wait too long for a bus.
The simulated buses will likely have achieved equal headways by the time you have read this far. Click anywhere on the simulation to remove one bus, leaving a large gap, and you will see that BusGenius restores equal spacing after any disruption, and without need for management intervention or coördination among the drivers.
Passengers like it because buses arrive more regularly.
Drivers like it because it frees them of the pressure of chasing a moving target.
Management likes it because BusGenius can deliver better service with fewer buses. And there are a host of other things to like, such as that there is no need to maintain a bus schedule. Furthermore, because BusGenius automatically senses changes and adjusts accordingly, buses can be added to or removed from the route at any time. In fact, the route itself can be changed (for example, to detour around construction). After any such a change the headways will automatically re-equalize to the shortest possible. If a manager wants even smaller headways, just add a bus; there is no need to wait for an open slot in a schedule.