Speed and distance estimation under simulated conditions

This paper reports two studies which investigate drivers' estimations of speed and distance under simulated driving conditions. In both cases constrained verbal estimates are contrasted with 'estimates' where the subject is required to change the distance or speed initially presented to the subject. In the distance judgement study, subjects saw a familiar or unfamiliar object, which was placed between 10 and 450 metres away. Subjects estimated how far away this appeared to be and then moved themselves, or another object, such that the distance was twice or half that initially seen. In the speed estimation study, subjects watched an initial speed, were then required to estimate how fast that speed was and then to change the display to show a speed which was half or double that initially seen. The initial speeds varied from 10 to 80 mph and were watched with or without accompanying digitised traffic noise. Subjects' ability to make speed estimations or productions solely on the basis of this auditory information was also studied. The results are discussed in terms of the differences between responding using the estimation and production paradigms, as well as the role played by auditory information on speed perception and self- other- motion and target familiarity on distance perception.