Calibration of the Bunched Exponential Distribution of Arrival Headways

The estimation of arrival headways is fundamental to the modelling of gap acceptance processes for estimating capacities of sign-controlled traffic streams, roundabout entry streams and filter turns at signalised intersections. It is also essential in modelling both vehicle-actuated signal timings and queuing at all types of intersections for performance prediction. This paper considers a class of arrival headway distributions known as negative exponential, shifted negative exponential and bunched exponential. A description of the bunched exponential arrival headway distribution is presented, and the results of its calibration using real-life data for single-lane traffic streams and simulation data for multi-lane streams are given. Examples of gap-acceptance capacities and delays predicted by different exponential headway distributions are also presented.