Updating turn probabilities at intersections in response to traffic incidents

Urban road traffic simulators sometimes require the turn probabilities at the intersections of the network they are simulating. This paper describes a method for updating the given probabilities following the occurrence of a traffic incident. We first estimate the origin and destination of traffic prior to the incident by computing an OD matrix (approximately) consistent with the given turn probabilities and an assignment reflecting the normal traffic conditions. Following the incident, we work backwards from this OD matrix and an assignment reflecting the changing conditions to determine a new appropriate set of turn probabilities. We extend the TRITRAM simulator to simulate the effects of incidents using this method, which we validate on the urban networks constituting TRITRAM’s test suite. Acknowledgements: This research was supported by the Cooperative Research Center for Advanced Computational Systems. Thanks to Garry Francis, Peter Lowrie, Ngoc Nguyen and Doug Quail from RTA Traffic Technology Branch, for their assistance in reviewing an extended version of the paper and suggesting some of the evaluation procedures. Thanks also to Melissa Dobbie and Jeff Wood from CSIRO for their help with statistics.