Abstract
This report concerned with the instability of the relationship between real speed and the sensation of speed experienced by the driver relative to the physical speed at which he is moving. The various contributing factors are outlined. Speed adaption is considered as a major factor responsible for errors in the driver's judgment of speed, and the hypothesis is made that by deliberately distorting the spatial geometry of the visual field it should be possible to counteract the effects of adaption. The results of this experiment carried out on a simulator confirmed the possible value of such a technique. Proposals are made for future research into the control of behaviour by the use of illusion particularly in the driving situation.