Effect of Vehicle-Mounted Message Boards on Move-Over Behavior: A Disaggregate Analysis Approach

Abstract: Across all fifty U.S. states, the District of Columbia, and Puerto Rico, drivers are required by law to move over when approaching emergency responder vehicles. Different types of treatments, which include message or arrow boards, cones, and vehicle lighting and marking, can be used to increase the compliance. This study examines the effectiveness of vehicle-mounted message boards such as messages, arrows, and caution symbols in encouraging compliance with these move-over laws. It focuses on how these messages affect driver perception and behavior, with the goal of identifying strategies that improve scene visibility and safety during roadside incidents.

The study collected data from over 4000 vehicles passing a staged roadside incident, at three locations in Florida. Of these vehicles, 2,108 traveled in the lane adjacent to the emergency response vehicle, necessitating a move-over action. A disaggregate analysis was used to assess how lighting and different message boards influenced the behavior of individual drivers.

The findings indicate that different messages influence driver move-over behavior. The use of an arrow board pointing to the left was the most effective treatment, outperforming the conventional changeable message board caution mode (4 Dots). Additionally, several factors, including location, visibility, the presence of heavy vehicles, traffic in adjacent lanes and downstream driving behavior, were found to influence driver compliance.

Based on these findings, the study recommends the use of directional arrow boards alongside conventional signage to improve driver compliance during roadside incidents. Furthermore, the analysis suggests that location-specific treatment adjustments can further optimize safety. The research also calls for revisions to the Manual on Uniform Traffic Control Devices (MUTCD) to provide clearer guidelines for using message boards during emergency situations. These changes would help tailor emergency response measures and address resource constraints which differ from those typically used in work zone settings.