Evaluating the Control Strategies for Freeway Variable Speed Limit Systems in PARAMICS: Selection of the Optimal Posted Speed Limit

摘要

The Variable Speed Limit (VSL) system is a dynamic freeway control system, which can be used to adjust the posted speed limit in response to the real-time traffic flow characteristics and weather conditions. The primary objective of this paper is to select the optimal posted limit of VSL on freeways by evaluating the effects of control strategies. A widely used microscopic simulation package, PARAMICS, was used and the control strategies were integrated into the simulation model through the Application Programming Interface (API) using C++ programming language. Eight control strategies were tested for their effects on traffic safety and traffic efficiency. The simulation results show that the optimal duration of intervention is 15 minutes , which allows most of the control strategies to reduce the crash potential. Compared to the non-VSL control strategy, the optimal posted speed limit under 15 minutes for intervention duration is 110km/h, which significantly reduces the crash potential, and does not increase the total travel time. The research results proposed in this paper provide transportation professionals some important and helpful information for selecting the optimal posted speed limit of Variable Speed Limits on freeways.