South Louisiana suffers numerous episodes of fog that often result in dense-fog advisories. Max-Planck-Gesselschaft reports a difference between navigating with a fogged windshield and driving in real fog. Researchers at the Institute for Biological Cybernetics in Tubingen, Germany, report that contrary to previous beliefs, drivers overestimate speed during foglike conditions. Virtual reality simulations determined drivers increase speeds in foglike conditions and underestimated them when visibility reductions did not depend on distance. Drivers registered an average speed of 52 mph during good visibilities and 42 mph in heavy fog. When visibilities were equally reduced, at all distances, with a fogged windshield, average speeds increased to 62 mph. Speed also can be overestimated at low contrasts of the surrounding scenery. The study suggests drivers should rely more on their vision.