Estimation of average vehicle time headway for light traffic

Vehicle time headway is one of the most fundamental microscopic characteristics of traffic flow. It affects roadway safety, capacity, and level of service. An estimated average time headway can provide an input to intelligent transportation systems for the online monitoring of roadway safety. Single inductive loop detectors are widely installed devices in road networks to regularly measure traffic volume and occupation. The purpose of this paper is to investigate the recursive estimation of average headway using the information from a single loop detector in the scenario of light traffic (e.g. during early morning or late evening period for most of the sections of motorways). A set of recursive estimation equations is developed with a nice and neat form using Bayesian analysis. The incurred computational cost for updating the estimate of average headway is kept to be a minimum. The developed method is illustrated using real traffic data. © 2010 ASCE.