Advanced traveler information system (ATIS) has been used and is viewed as an essential component for present-day traffic management. ATIS may provide information such as the traffic situation, incidents, and weather conditions which may adversely affect traffic. This information may be disseminated through media such as radio, television, internet, mobile phone, dynamic navigation device, and the variable speed limit (VSL) system. The main objective of this dissertation was to examine whether traffic information, provided by VSL systems and real-time traffic information (RTTI) for navigation systems, are consistent with each other. Before the comparative analysis, methods for evaluating different features of VSL systems were developed. A VSL system is expected to detect incidents and take measures to avoid crashes, postpone, or alleviate congestion by providing advance warning messages and/or harmonize traffic by reducing speed differences between vehicles. Methods for assessing three features of VSL systems, namely, incident detection, warning, and harmonization efficiency are presented. For the purpose of evaluating incident detection, the traffic state was reconstructed from dual loop detector data, discretized, and compared with the message signs of the VSL. Warning efficiency was assessed by generating virtual vehicle trajectories and determining whether a driver experienced adequate warning. Scenarios for message signs and their influence on traffic safety were identified according to the distance of the warning from the tail of the congestion. Weightings for detections and missed detections based on the different scenarios were developed. A quality evaluation method was then used to grade the levels of the system in their incident detection and warning efficiency. Two approaches, based on the ability of the system to reduce inhomogeneity in the traffic stream and improve the consistency (proper coordination) of the displayed speed limits were proposed for harmonization assessment. Inhomogeneity in the traffic stream was checked by identifying the traffic state and assessing the ability of the system to reduce the speed differential in the metastable traffic state (i.e., flows > free flow, but with speeds > congestion speed). The coefficient of variation (CV) was employed to quantify the standard deviation of speed. Consistency was assessed by observing the consecutive dynamic changes in the displayed speed limits as drivers traverse the route. This was done by reconstructing the traffic state, generating virtual trajectories based on the reconstruction, and finally tracking the virtual vehicles to reproduce the sequence of speed limits that drivers would have experienced. For the comparison between VSL and RTTI, firstly, a qualitative analysis was done to understand and provide insight into the characteristics of the two information sources. The evaluation was made by obtaining the differences in speeds between the discretized space-time representation of reality and the space-time traffic information displayed by the VSL/RTTI. The discretization ensured that the method takes into accounts, limitations faced by the providers in broadcasting the information. The quantitative comparative analysis was also made by superimposing the space-time areas of reality to the space-time areas of the information broadcast. However, a predictive buffer was introduced in the assessment. The predictive buffer was considered as areas of traffic information which could be considered as advance warning messages, or rightly predicting and giving congestion information prior to the onset of actual congestion, which otherwise would have been taken as false alarm. 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 real world problem to prove its applicability. The site for the case study was the autobahn A99, near Munich, Germany.    «

Advanced traveler information system (ATIS) has been used and is viewed as an essential component for present-day traffic management. ATIS may provide information such as the traffic situation, incidents, and weather conditions which may adversely affect traffic. This information may be disseminated through media such as radio, television, internet, mobile phone, dynamic navigation device, and the variable speed limit (VSL) system. The main objective of this dissertation was to examine whether t...    »