Variable message signs (VMS) are programmable traffic control devices that convey nonpersonalized real-time information on network traffic conditions to drivers encountering them. Especially useful under incidents, VMS aim to influence driver routing decisions to enhance network performance. This study investigates the effect of different message contents on driver response under VMS. Presumably, if the message content is a significant factor in driver response, the traffic controller can use it as a control variable to influence network traffic conditions positively without compromising the integrity of information. This issue is addressed through an on-site stated preference user survey. Logit models are developed for drivers’ diversion decisions. The analysis suggests that content in terms of the level of detail of relevant information significantly affects drivers’ willingness to divert. Other significant factors include socio-economic characteristics, network spatial knowledge, and confidence in the displayed information. Results also indicate differences in the response attitudes of semitrailer truck drivers compared to other travelers. They provide substantive insights for the design and operation of VMS-based information systems.

This study investigates driver response attitudes to traffic information provided through variable message signs (VMS). It develops VMS driver response models using stated preference data collected through three different survey administration methods: an onsite survey, a mail-back survey, and an Internet-based survey. In the process, it highlights the strengths and limitations of each method in eliciting driver response attitudes to information provision. The use of different media for the survey administration provides insights for the design of travel surveys. A key study focus is to evaluate the effectiveness of Internet-based surveys for analyzing driver behavior under information provision. The results illustrate that a combination of survey administration methods may generate more representative data. They also indicate a high correlation between VMS message type and driver response. This suggests message content as a control variable for traffic system operators to trigger optimal routing policies under congested conditions to improve network performance. The paper highlights the benefits afforded by Internet-based surveys in the study context. They are cost-effective, amenable to automation, less laborintensive, can target certain market segments more effectively, and can enable greater clarity in the survey through better visual articulation. However, their widespread use requires greater market penetration in terms of Internet access.

Prepared in cooperation with the Indiana Department of Transportation and Federal Highway Administration. AbstractThis study addresses the issue of whether the message content of variable message signs (VMS) can be used as a control variable to favorably influence traffic conditions in real-time. The focus is on the level of detail of information displayed on the VMS, and not human factor issues. It implies an understanding of driver sensitivity to information content. Also, for real-time implementation, the displayed information should be consistent, timely, and reliable. A framework is developed for optimizing system performance under incidents using the VMS message content as the primary control parameter. It consists of: (i) an efficient control strategy to enhance system performance using the VMS and information on current traffic conditions received from on-line sensors; (ii) a driver response model to supplied information that addresses the effect of the message content on drivers' en-route switching decisions; and (iii) an incident clearance time prediction model which predicts the expected delay due to an incident. Key Wordsvariable message signs, real-time incident management, advanced traffic management systems, simulation-based optimization, consistent route diversion models, internet-based driver survey, incident clearance time prediction model. Distribution StatementNo restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161 as part of information-based real-time advanced traffic management systems (ATMS) to enable travelers to make more informed pretrip and en-route route choice decisions. The effectiveness of the VMS strategy in enhancing travel conditions, especially under incidents, depends on driver attitudes and response behavior under the messages displayed. This highlights the importance of the content of the VMS messages displayed and the need for coordinated and consistent control strategies by the system controller. The primary focus of this study is to develop a mechanism to determine the VMS messages to be displayed that enhance system performance and are consistent with driver response behavior.To enable effective VMS-based incident management, a framework for optimizing system performance was developed using the VMS message content as the control variable. It consists of simulation-based algorithms to determine the optimal VMS messages to be displayed, driver response behavior models under the displayed VMS messages, and an incident clearance time prediction model to estimate the incident duration. The driver behavior models were classified into freight truck and non-truck categories to differentiate between the response attitudes of freight truck drivers and other travelers vis-a-vis en-route route diversion.The Borman Expressway corridor in northwest Indiana was used as a case study to develop the driver response behavior models and the incident clearance time prediction model. Simulation-based off-line testin...