The Effects of Traffic Accidents on Travel Time Reliability

Traffic accident is one of the main causes of the increasing congestion in traffic networks. Due to the fact that traffic accidents reduce the capacity of a freeway and that their effect and duration are rather unpredictable at the moment they occur, it is expected that they contribute for great proportion to less reliable travel times. In this paper we present an empirical travel time reliability analysis on a basis of a large dataset of registered traffic accident data and empirical traffic flow data. The preliminary results show that travel time accidents result in both higher travel time variability and higher probability of traffic breakdown on freeways and thereby higher travel time unreliability.