The goal of this study was to provide information about the frequency of installation and use of fog lamps. Two surveys were performed. In the first one, installation of fog lamps was estimated by a survey of parked vehicles in two iarge shopping centers. The second survey studied the usage of fog lamps during daytime and nighttime, under clear, rainy, or foggy conditions. In this survey, an observer in a moving vehicle noted the types of lamps that were energized on the fronts of oncoming vehicles, and whether fog lamps were installed at all. The main findings are: (1) The best estimate of the current frequency of installation of fog lamps in southeast Michigan is about 13%. (2) During daytime, the usage of fog lamps increased with deterioration in atmospheric conditions, with the usage reaching 50% of all installed fog lamps during moderate-to-heavy fog. This indicates that, during daytime, drivers adjust the usage of their lamps in response to atmospheric conditions, probably more to increase the conspicuity of their own vehicle than to illuminate the road ahead. (3) During nighttime, the usage of fog lamps was rather high (around 63% of fog lamps installed). However, the usage does not appear to be influenced by the presence of fog or rain. This implies that, during nighttime, fog lamps are used to supplement low beams in general, rather than to provide lighting adapted to atmospheric conditions. (4) When fog lamps were used during daytime, they were seldom used alone, without standard headlamps. During nighttime, fog lamps were never used alone. This pattern of nighttime usage is consistent with the Society of Automotive Engineers Standard J583, and with the intent of the laws of the State of Michigan. However, this pattern of usage might limit the potential benefits that could be achieved in heavy fog with well-designed fog lamps used without standard headlamps.