Investigating Limits of Benefits Provided by Variable Message Signs in Urban Network

A major objective for providing real-time traffic information to drivers is to improve the efficiency of the road network, especially in incident situations. However, the subsequent effects depend on behavioral response, in both interpreting available information and reacting to it. Research focusing on the use of variable message signs (VMSs) was done in the urban network of Southampton, in the United Kingdom, a site chosen because of the innovative large-scale application of an urban VMS system and the availability of traffic data derived from urban traffic controls using the split-cycle offset optimisation technique (SCOOT) and other detectors. Although previous research regarding VMSs located in inter-urban areas such as motorways is well documented, the use of VMSs within urban areas is not widespread. The research analyzed several case studies by using detector data collected during incident scenarios at seven locations to assess driver response to VMS messages in terms of diversion rates. Positive driver responses were measured for all, with diversions ranging from 2% to 30%, although not all were solely attributable to VMS information. No relationships between the severity of VMS message and driver response could be identified. A simulation model was then used to quantify the potential network benefits of traffic information. A main finding was that if the diversionary route had sufficient spare capacity, substantial VMS benefits were potentially attainable, although these benefits were not distributed equally.