Assessing the Message Design on Variable Message Signs in Mitigating the Bottleneck Issue at Work Zones

In this study, drivers’ preferences of and responses to text and graphic road sign messages at work zones were analyzed in an attempt to reduce the bottleneck conditions at lane-reduced work zones. Advisory messages associated with three driving advisory conditions (DACs), “Merge to the Right Lane,” “Zip Merge” (vehicles take turns), and “Continue Travel Normally,” were assessed through a questionnaire survey and driving simulation to seek the best messages in advising drivers in different traffic conditions when approaching work zones.

A questionnaire survey was first deployed to identify participants’ preferences towards a series of messages posted on variable message signs (VMSs). Participants rated each message from one to five as to their effectiveness in advising drivers in different conditions. Between the highest rated text and graphic messages under each DAC, participants gave their preferences toward either text or graphic messages. A total of 81 subjects participated in the survey. Survey results indicated that text messages were strongly preferred over graphic messages in all DACs.

The effectiveness of several top rated messages identified in the survey was further assessed through a driving simulation. Various text and graphic messages were posted on portable VMSs along a straight freeway in a fix-based driving simulator. Subjects were asked to verbally respond with a number when they identified a message, denoting the DAC associated with that message. It was found that graphic messages were most effective in all three DACs in terms of response time and accuracy. Recommendations for messages in each DAC were made.