Traffic incidents, such as an accident or a broken down vehicle, cause more than half of all congestion delay and are often responsible for a number of secondary accidents. In response to these effects, incident management (IM) plans have been developed and implemented in many countries. However, traffic management during the incident is usually the weakest link in the IM plans. This paper reports on the development of a microscopic simulation model, SITRAS, which is intended to be used in the preparation and investigation of incident management plans. One promising management measure during traffic incidents is the use of variable message signs (VMS) to inform drivers about the traffic conditions in real time. Several studies have shown that the diversion rate at VMS sites is highly dependent on a number of factors including the message content displayed on the VMS. If the diversion rate for various message contents can be predicted, this can be used as a valuable traffic management tool during incidents: a simulation model can estimate the 'optimum' diversion rate for any incident scenario, then the appropriate message content can be selected which would be most likely to generate the required diversion response from motorists. This paper presents a review of the literature on VMSs and their effects on traffic, then it describes the concepts developed for modelling route diversion in response to VMSs in SITRAS. The last section summarises the findings and outlines further steps of the work currently in progress. (Author/publisher) For the covering entry of this conference, please see ITRD abstract no. E205861.
Abstract