Inclement weather adversely affects traffic conditions, resulting in substantial roadway congestion caused by decreased free flow speed, capacity, and saturation flow rate due to low visibility and/or slippery pavements. To mitigate the weather-caused traffic congestion, several weather responsive traffic management (WRTM) strategies have been proposed. The WRTM can be classified into advisory, control and treatment strategies. This paper evaluates the performance of a variable message sign (VMS)-based advisory WRTM strategy and quantifies its impacts by using a mesoscopic simulation-based Dynamic Traffic Assignment (DTA) model utilizing DynusT.
Two case studies examining the impact of VMS under a plausible inclement weather condition are conducted. In doing so, a DynusT-based network modeling an urban area including a major interstate highway and several signalized arterials is calibrated based on normal day field data such as travel times and traffic counts. Based on the inclement weather condition, the parameters of supply models and demands of the calibrated network are adjusted to reflect the impact of the inclement weather.
The first case study result shows that while the impact of VMS on the entire network appears not significant, those travelers, followed the VMS advisory information, reduced their travel times by 18 to 29 percent. In addition, the second case study reveals that the locations of VMSs significantly affect the performance of VMSs, resulting in maximum 16% travel time saving while no significant impacts are found on the number of VMSs.