Why do buses bunch?
Click and hold a bar below to delay its respective bus. Note how even a short delay causes the buses to bunch together after a while.
Hover over a stop to see its history. The area of the curve is cumulative wait time. Bunching makes the area grow.
Have you ever been waiting for a late bus, and all of a sudden two or three buses arrive at the same time? That's called bus bunching.
Bus bunching happens because, if a bus gets delayed, then there will be more people waiting at the next stop than anticipated. The extra passengers' boarding time makes the bus even later, and so on in a vicious cycle.
To combat bus bunching, bus sytems have to build slack into the system, but that slack involves extra buses and labor and longer travel times.
