Effects of Emergency Vehicle Warning Lighting System Characteristics on Driver Perception and Behavior

Secondary crashes, including struck-by incidents are a leading cause of line-of-duty deaths among emergency responders, such as firefighters, law enforcement officers, and emergency medical service providers. The introduction of light-emitting diode (LED) sources and advanced lighting control systems provides a wide range of options for emergency lighting configurations. This study investigated the impact of lighting color, intensity, modulation, and flash rate on driver behavior while traversing a traffic incident scene at night. The impact of retroreflective chevron markings in combination with lighting configurations, as well as the measurement of “moth-to-flame” effects of emergency lighting on drivers was also investigated. This human factors study recruited volunteers to drive a closed course traffic incident scene, at night under various experimental conditions. The simulated traffic incident was designed to replicate a fire apparatus in the center-block position. The incident scene was complemented with a cone taper extending from the driver-side buffer to the edge of the roadway. The results indicate that higher-intensity lights were judged consistently as more glaring, but were only rated as marginally more visible. The rated visibility of the lights appears to be related to the perceived saturation of the color, while discomfort glare is related to the amount of short-wavelength spectral content. The results also suggest that the presence of highly reflective markings may decrease drivers’ ability to see first responders working adjacent to their vehicles.