Abstract
Traveler Information Systems are designed and operated by public transportation agencies to provide travelers with real-time traffic information, enabling them to make better travel decisions. The most commonly used way to provide real-time en-route traveler information to motorists is though Dynamic messages signs (DMS). Despite their effectiveness, they are costly and limited in the amount of information they can deliver. The wide availability of smart mobile devices communication technologies offers the possibility to provide traveler information not only through in-vehicle devices without incurring huge infrastructure costs, but also in a more flexible manner to selected individuals and locations without geographical constraints. To comprehensively develop and evaluate this concept, this research was carried out from three perspectives.
First, this research proposed the concept of VDMS (Virtual Dynamic Message Signs) prototyped a smartphone based application for demonstration and understanding of user experience for future deployment. The user survey reveals a positive attitude among participants toward VDMS in terms of both usefulness and satisfaction, with an average rating of -0.90 and -0.81 on a -2 to 2 (Totally agree to Total disagree) five point Likert scale. The survey also indicates that potentially most drivers (80.95%) perceive that VDMS is a safer way to receive information and most drivers (66.67%) feel more comfortable receiving information from VDMS compared with DMS. The results indicate great user acceptability and potentials for such systems to be deployed by public agencies in the future.
Second, since the concept of VDMS uses in-vehicle devices, particularly relying on auditory messages to deliver DMS-type messages, this research aims to address the question whether this new way of information delivery conveys information as least as effectively as existing DMSs. A mixed repeated measure experiment was designed using a driver simulator to examine the impacts of driver age, information transmission mode, amount of information, and driving complexity on message comprehension, distraction and perceived difficulty. Forty-two Participants were recruited and each of them was tested under different combinations of the three within-subject factors. Participant performance was measured in terms of message comprehension, distraction, and self-reported message difficulty level. Results reveal that VDMS generally performs better than DMS across different amounts of information and under different driving conditions, regardless of driver age. VDMS is significantly better than DMS in message comprehension under relatively complex conditions, reduces reaction time to unexpected stimuli (as measured with a reduced time-to-brake of 0.39 seconds), and makes the same messages easier to process and retain for drivers than DMS. Based on these results, it is recommended that transportation agencies give careful consideration to VDMS as a future strategy for delivering public traffic information in a connected vehicle environment.
Finally, with VDMS as a new powerful tool for public en-route traveler information provision, the study selected, among its many potential applications, routing advisory for emergency traffic management as an example, developed and evaluated corresponding Personalized System Optimum Information (PSOI) strategy, to demonstrate potential benefits of advanced management strategies enabled by VDMS. An efficient queue-based heuristic algorithm was developed for generating VDMS-PSOI routing advisories, in particular considering mixed information use in the traffic network to accommodate the adaptive behavior of other users in the network. Case studies indicated that heuristic algorithm was effective, and existence of PSOI can help shorten average travel times for all types of travelers, with maximum benefits obtained after a certain market penetration (75% in our case studies). Also, PSOI advisories were not only effective in reducing average system travel time, but also guarantee relatively short personal travel time even compared with user-oriented information groups. Thus, PSOI is recommended by this paper as an advantageous way for next generation advanced information systems enabled by VDMS, particularly for emergency traffic management by Traffic Management Centers.
