Improving the Ability of Drivers to Avoid Collisions With Snowplows in Fog and Snow


Albert Yonas, Lee Zimmerman

July 2006

Report no. Mn/DOT 2006-29

The goal of this work is to understand how the processing of motion under the conditions created by blowing snow causes drivers to fail to detect that they are approaching a vehicle ahead. Color was examined under blowing snow conditions to assess whether an equiluminant (equal brightness) situation was created. In this situation, contrast in light level is not detected but differences in color are. When an equilument situation is created by snow, a perceptual illusion lowers the ability to perceive approach. The results indicate that colors in the red-yellow part of the spectrum can create a dangerous equiluminant situation in blowing snow and fog. We were unable to find an optimum color to paint snowplows to make them less susceptible to rear-end collisions. Perception studies investigated the ability of the visual system to detect the expansion pattern that drivers use to perceive that they are approaching a vehicle. We found that low contrast created by a snow cloud greatly reduces the ability to perceive approach. Flashing lights that increase conspicuity, substantially decreased the chances that a driver will be able to avoid a crash. Additional ways to improve the placement of warning lights based on these findings were proposed.

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