Self-equalizing headways reduce bus-bunching

The primary challenge for an urban bus system is to maintain constant headways between successive buses. Most bus systems try to achieve this by adherence to a schedule; but this is undermined by the tendency of headways to collapse, so that buses travel in bunches. To counter this, we propose a new method of coördinating buses. Our method abandons the idea of a schedule and even any a priori target headway, and instead focuses on equalizing headways. Our method is self-managing: It allows the natural headway of the system to emerge spontaneously; and after disturbances it reëqualizes headways without intervention by management or even awareness of the drivers. We report on a successful implementation to control a bus route in Atlanta.