Evaluation of Light-Emitting Diode Warning Beacons for Maintenance Vehicles

Rotating warning beacons containing filament light sources have long been used on highway maintenance vehicles to indicate the presence of the vehicle to other drivers. Flashing warning beacons containing light-emitting diodes (LEDs) are beginning to be used in place of rotating warning beacons, in part because they use considerably less power. To help ensure that LED warning beacons will provide a comparable warning signal to drivers who approach vehicles outfitted with them, the photometric and temporal characteristics of LED warning beacons were measured and compared with data on human response time. In addition, several LED warning beacons were compared with a conventional incandescent rotating warning beacon in regard to the distance at which observers could detect that a vehicle had moved closer. Pairs of LED warning beacons provided closure detection distances that were equivalent to pairs of conventional rotating beacons. Although single LED warning light configurations were not tested, the pairs of LED beacons that were tested reliably outperformed a single conventional beacon configuration for both energy use and closure detection distance. Results suggested that LED warning beacons provide comparable visual information to other drivers and use substantially less power than conventional rotating beacons do.