Impacts of Flashing Emergency Lights and Vehicle-Mounted Illumination on Driver Visibility and Glare 2019-01-0847
Flashing emergency lights on police cars, fire trucks, and ambulances need to be bright enough to alert otherwise unaware drivers about their presence on and near the roadway. Anecdotal evidence suggests that public safety agencies select emergency lighting systems with red and/or blue flashing lights based on their apparent brightness, with brighter lights judged as "better." With the advent of light emitting diode (LED) emergency lighting systems producing highly saturated colors and using relatively little electrical power, some reports have suggested that flashing emergency lights can sometimes be too bright, causing distraction or disability glare and making first response workers less visible by oncoming drivers. Indeed, these workers are at higher risk for being injured or killed in vehicle crashes. In the present study, participants viewed red and blue flashing lights on a scale model police vehicle, conforming to present recommended practices for emergency lights. Lights varied in intensity and optical power. Participants were asked to view the scale model police vehicle and identify whether a figure of a police officer was standing on either side of the vehicle. In some trials, white LED sources were energized, providing low-level illumination on both sides of the vehicle, near the possible locations of the police officer. In some trials, no police officer was present. Participants identified the location of the police officer, if any, as quickly as possible. Although the blue lights were rated as glarier than the red lights even when matched for intensity, the location accuracy for the police officer was unaffected by the color of the lights. The presence of low-level white illumination drastically improved accuracy.
John Bullough, Nicholas Skinner, Mark Rea