Impact of Work Zone Warning Light Configurations on Driver Behavior

The Move Over Law (Minnesota Statute 169.18, Subdivision 11) recognizes the impact that lane choice has on worker safety by requiring drivers to move at least one lane away when passing a parked emergency vehicle, freeway service patrol vehicle, road maintenance vehicle, or construction vehicle with its warning lights activated. The Minnesota Department of Transportation’s (MnDOT’s) standard warning lights on maintenance vehicles have traditionally been incandescent amber double rotators. These lights are not very bright or flashy and have not produced the desired impact on driver lane choice. MnDOT staff were eager to determine which lighting alternatives made the most sense for replacing the double rotator configuration. Existing instrumentation on one of MnDOT’s highways provided the perfect opportunity to evaluate the options. Using lane and speed data from a surveillance system aimed at preventing intersection crashes, MnDOT evaluated eight different lighting alternatives (including a variety of LED and blue light configurations) to determine the most effective lighting option for slowing down traffic and moving vehicles away from workers. This report describes the lighting configurations evaluated, the impacts of each on driver behavior, and the steps that MnDOT has taken to modify lighting policies as a result of the research findings.