Simple Model of Forward Visibility for Snowplow Operators Through Snow and Fog at Night

Backscattered light reflected from falling snow, rain, and fog impairs visibility and can hinder performance of snowplow operators. New York State Department of Transportation snowplow operators cite backscattered glare as an important problem, and many drivers use their own “solutions” to counteract it. A literature review yielded two important conclusions: backscattered light from a lamp in fog and falling snow is reduced, and visibility is improved (a) as the lamp is moved away from the operator’s line of sight and (b) with a narrow-beam lamp. Field tests of lighting configurations during inclement weather were conducted to determine the effects of beam type and displacement from the operator’s line of sight on visibility, glare, and satisfaction. On the basis of these data and the literature, a simple mathematical model was developed that predicts the forward-visibility ratings of snowplow operators. This model can be used to guide specifiers in selecting light sources and mounting locations for snowplow operations.