Effectiveness of VMS Messages in Influencing the Motorists' Travel Behaviour

The variable message signs, abbreviated as VMS messages, are disseminated through LED displays to provide the travelers and motorists information, warning and guidance on the current traffic situation. As an advanced traffic guidance system, the VMS messages help drivers to choose the routes with lower traffic volumes. Thus, the vehicles can be more evenly distributed in the road network to improve the performance of traffic system and reduce traffic delays. To this end, the VMS technology has been widely used in the expressways of Singapore. This paper aims to evaluate the immediate impact of VMS on the overall traffic distribution of Singapore in response to accidents and obstacles. For this purpose, we consider the incidents data and their corresponding VMS messages from the two busiest expressways of Singapore, namely Pan Island Expressway (PIE) and Central Expressway (CTE). For this analysis, we ignore the VMS messages of the locations which are already congested due to traffic incidents, since the motorists may be influenced by the congestion and not entirely by the VMS messages. The next step is to obtain the locations of other VMS displays and their nearby downstream exit points. The central argument of this analysis is that if the average traffic flow of the exits increases significantly compared to that of normal days, it demonstrates the impact of the VMS messages on the drivers' behavior. Our results show that the average outgoing traffic flow from the expressways towards the exits increases by 14% after the VMS messages have been activated.