When the sun is low in the sky, a driver headed directly towards the sun is subject to glare, which impairs target detection. Unobtrusive (video) observations of drivers approaching a setting afternoon sun found only a small decrease in speed compared with a non-glare condition; in addition, speed variability appeared to increase somewhat in the sun condition. These effects, which are similar to what has been reported for driver behavior in fog and other impaired-visibility conditions, increase the risk of accidents. Causes and implications are discussed in the paper.

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