How's this for the fog of war? --MW Fog Alters Perception Of Speed LONDON (Reuters) -- Fog can trick drivers into thinking their speed is far slower than it actually is, according to a paper in the April 2nd issue of the journal Nature. Researchers from the University of Wales, Cardiff, UK, report on experiments in which subjects were asked to respond to different virtual driving environments in a driving simulator. Robert J. Snowden and colleagues first presented the subjects with two scenes, one that was clear and another that was either clear, misty or foggy. The scenes had been adjusted to be moving at the same speed, but the subjects perceived the foggier scenes to be moving more slowly. The subjects were then asked to achieve a target speed in different driving conditions. The researchers found that the subjects drove at higher speeds as the scene became more foggy. Snowden and colleagues note that drivers tend to rely more on their own perceptions -- rather than the speedometer -- in foggy conditions because they are watching the road intently for emerging objects. "Hence it is exactly in conditions of reduced visibility caused by fog that drivers rely on their own perceptual judgment of speed," write the researchers. To explain their findings the study authors cite the results of previous research, which suggested that the level of contrast seen by the human eye affects the way it judges speed. As contrast decreases, as it does in fog, objects appear to move more slowly. The researchers conclude that the blame for many accidents in fog "...may not lie solely in the irresponsible nature of the drivers but with an unfortunate quirk of our perceptual systems." SOURCE: Nature (1998;392:454)
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