The influence of visual pattern on perceived speed.
The two experiments to be described are concerned with the instability of the relationship between objective and subjective speed as experienced by the driver of a motor vehicle. A number of factors that contribute to the instability are outlined, one of the most important of which is considered to be rectilinear speed adaptation. The hypothesis is made that by deliberately distorting the spatial geometry of the visual field it should be possible to counteract the effects of sensory adaptation. The first experiment tests the hypothesis on a motion simulator and confirms the possible value of such a technique. The second experiment describes a field study in which the proven technique is applied to a stretch of motorway at a site where the accident rate was exceptionally high owing to excessive speed. The observed reduction of relevant accidents at this and a number of other motorway sites where the system has been installed is discussed.