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Transportation Safety

Cable median barriers on the highway.
Department of Transportation

Transportation Safety

Effectiveness of Crash Fact/Safety Message Signs on Dynamic Message Signs

Project Number: SPR-1686

Contract Number: 2019-0295

Status: Complete

Start Date: 03/15/2019

End Date 06/30/2021


From 2010 to 2020, transportation agencies have increasingly used roadside dynamic message signs (DMS) to display safety messages. Despite their widespread use, evaluations as to potential impacts on driver behavior, and the resultant impacts on traffic crashes has been very limited. This study evaluated the use of DMS to display safety messages leveraging data from public commentary, opinion surveys, crash statistics, and field studies of driver behavior. Public opinion was largely split as it relates to the appropriateness of using DMS for safety messages. A statewide survey showed that the majority of respondents had seen a DMS, but only 25 percent indicated that such messages improved their driving behavior. A series of crash analyses were conducted to assess relationships between various types of crashes and the frequency with which safety messages were displayed. The results did not show significant differences with respect to total or nighttime crashes based upon the frequency of pertinent safety messages. Speeding-related crashes were significantly lower downstream of DMS that showed higher numbers of messages related to speeding or tailgating. The crash data analysis was complemented by a series of field studies that sought to determine the immediate impacts of safety messages on fundamental aspects of driving behavior. Separate field evaluations were conducted to assess driver compliance with messaging related to the state's move-over law for emergency and service vehicles, as well as compliance with the posted speed limit. In general, the type of message displayed had minimal impact on driver behavior. However, an exception was that drivers were likely to drive at or below the speed limit when targeted move over messages were shown as compared to standard travel time messages. Both speed and lane compliance were improved for all message types if the roadside vehicle was a police car. The findings and conclusions from this research provide MDOT with insights to inform future policies as to the use of DMS for safety messaging.





Research Manager Project Manager Performing Organization 
Staff photo of Michael Townley  Project Manager Mark Bott  Michigan State University logo
 Michael Townley  Mark Bott  Michigan State University