The effect of sensory restriction upon perception of driving speeds at thirty miles per hour and below.

Previous research into driving safety has indicated that drivers often cannot correctly judge speed. The present study was conducted to investigate the perception of speeds from 5-30 mph and to examine the role played by vision and audition in this perception. Twelve university students served as Ss by being passengers in a car under the conditions of normal, no sight, restricted hearing and no sight plus restricted hearing. Under each condition speed estimates were made at 5, 10, 15, 20, 25 and 30 mph. The results were analysed using both algebraic and absolute error values which were expressed in terms of mph deviation as well as in terms of percentage inaccuracy. The no-sight condition was found to produce more error when algebraic values were used, these errors being overestimates of actual speeds. Higher speeds produced greater error when mph inaccuracy (both algebraic and absolute) was the measure and at lower speeds more inaccuracy in speed estimation was found in terms of percentage values of absolute error. The restriction of hearing alone or in addition to blindfolding of the Ss did not result in greater inaccuracy of speed estimation. The results are discussed in light of the findings of earlier studies.