| For many years, Intelligent Transportation Systems (ITS) have been promoted as an effective means to increase the safety and efficiency of the transportation network. One advanced transportation technology that has been widely adopted by many jurisdictions around the world is the Variable Message Sign (VMS). The intended purpose of most VMS systems is to display traffic related information to assist drivers in making informed choices about their travel routes and advise them of any delays in the traffic. They have been widely used in major expressways and arterials in many cities and are increasingly being deployed in work zones as well. The efficacy of providing traffic and other information has been a topic of constant debate. The papers in this special issue reexamined some of the research questions arising from the provision of information via ITS in general and VMS in particular.
CW Lee and colleagues evaluated, the satisfaction drivers derived from the travel information provided by VMS, using fuzzy aggregation. Application of fuzzy aggregation to analyze driver satisfaction allows one to represent the variability and complexity of human perception with great fidelity. Using the Nam-Mountain Tunnel advanced traveler information system as a case study, they evaluated drivers' satisfaction of delay information and travel time information provided by the VMS. The evaluated overall satisfaction was 0.65 for delay information and 0.63 for travel time information, indicating that drivers were moderately satisfied with the information provided. These satisfaction scores were somewhat smaller than those obtained from the conventional method using simple averages and assuming that the linguistic scale used for collecting the data was deterministic.
One of the determinants of drivers' satisfaction of the information is the format in which the information is provided. Choi and Tay argue that the use of pictograms is preferred over text messages because they are easy to read and comprehend in fast moving traffic and thus are more suitable for specialized VMS like lane control systems. They compare the existing pictogram designs which are largely adapted from Japanese and American designs with the designs adapted from Europe and those that are developed in Korea. Their study showed that not all locally developed signs were rated higher for their ease of reading than those designed overseas which suggested that some design characteristics were more salient whereas others tended to be more dependent on the local context. Therefore, it is important to conduct simple experiments and exploratory research to find the optimal designs to use and not simply adopt an existing design from overseas or assume that locally designed signs would be easier to read and comprehend by drivers.
JS Lee evaluated three information provision strategies: user optimum [UO], system optimum [SO] and mixed optimum [MO]. He used a simulation-based dynamic traffic assignment model at the mesoscopic level to simulate traffic flow on the road network. This model was integrated with a traffic management model that set traffic information and traffic signal strategies. Traffic information was assumed to be provided to minimize the travel cost for driver (user optimum), the network as a whole (system optimum), or a mix of the two strategies. He found that when traffic managers provided information for drivers using the UO strategy and drivers followed the information absolutely, the total travel time might even increase more than the case of no information. Such worsening occurs when drivers switch their routes and face congestion on the alternative route. This phenomenon is a new 'Braess Paradox ' in providing traffic information to drivers.
In a related article, Golly et al examined the provision of traffic information at work zones. A micro-simulation model was developed and applied to an interchange project in Calgary, Canada. One of the objectives of the study was to determine the diversion rates that would result in an effective work zone ITS deployment using VMS. Their results showed that diversion rates of 10% or less yielded a positive impact on network travel time and environmental benefit, whereas a higher diversion rate would produce negative effects due to over reaction in heavily congested networks during peak hour operation.
Tay and deBarros examined drivers' perception of the use of VMS for providing a variety of different information and messages. They conducted a qualitative focus group and a questionnaire survey of drivers aimed at examining drivers' perceptions and their self-reported reactions to the different types of messages displayed. In general, drivers support the use of VMS for traffic incident reports and weather information which have an impact on traffic delays and level of service. They also think that it is a good idea to display road safety messages and to remind drivers to drive safely and be courteous on the roads. Moreover, most drivers report that they do read and think about the messages displayed and do react positively to some of the road safety messages. Therefore, even though the VMS are originally installed for conveying traffic related information, they can and should be used to display other types of messages to increase their utilization and efficiency.
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