Winter maintenance vehicles for snowplowing often operate when visibility is compromised. Rear lighting on snowplows serves two purposes: to alert drivers of nearby vehicles that the snowplow is on the roadway, and to provide cues to those drivers about the snowplow's relative speed and distance. Flashing and strobing lights have been used on snowplows by many departments of transportation, who consider these lights as having high conspicuity and attention-getting properties. However, most accidents involving snowplows are rear-end collisions by other vehicles, and previous research supports the idea that flashing or strobing configurations are less effective than steady-burning lights at providing cues about relative speed, distance and closure to drivers approaching a snowplow from behind. To test this concept, a prototype steady-burning light bar using light-emitting diodes was developed and tested on a snowplow vehicle, which was also equipped with conventional flashing lights. The ability of subjects following snowplows to detect deceleration of the snowplow was measured with each lighting configuration during nighttime field tests conducted while snow was falling. The mean time to detect closure was significantly shorter with the steady-burning light bar than with flashing lights. Subjective ratings of visibility and confidence for judging speed and distance were also higher with a steady-burning light bar than for the conventional system.
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Flashing lights will be perceived as having higher brightness than steady-burning lights....