Empirical evaluation of real-time traffic information for in-vehicle navigation and the variable speed limit system

Advanced traveler information systems (ATIS) present traffic information to travelers to assist them in planning their journeys and also provide guidance when on the road. Providing travelers with information affects travel behavior and can result in improved performance and reduced congestion and emissions. However, the success of ATIS depends on, among other factors, whether drivers consider it useful and their particular responses to the provided information. There are, currently, many sources and market players in the traffic information industry producing traffic reports for consumers. The main objective of this paper was to examine whether traffic information provided from different sources are consistent with one other. A variable speed limit system and real-time traffic information system for in-vehicle navigation systems are used as a case study. This comparative analysis was made by superimposing the space-time regions of ground truth measured traffic conditions (“reality”) over the space-time regions of the reported information broadcasts. A predictive buffer was also introduced in the assessment. The predictive buffer was included to account for traffic information which could be considered as advance warning messages or correctly predicting and giving congestion information prior to the onset of actual congestion, which otherwise may have been reported as false alarms. This was motivated by the fact that optimal control approaches include the prediction of congestion in their control strategies. The methods developed in this research work have been applied to a real world problem to prove its applicability.