A Subjective Scale of Speed when Driving a Motor Vehicle

Abstract

An experiment is described which attempts to establish a subjective scale of speed, or more precisely of passive locomotion, such as that experienced by the driver of a motor vehicle. By a method in which the subject is required to produce a speed which in his opinion bears a given proportional relation to the standard speed presented, speed expressed as a sensation Φ and real speed S are tested for a possible power law relation of the form Φ = KSn. It is found that n is not a constant, but has a definite correlation with speed. The time taken by subjects to change from one speed to another is also positively correlated with speed. The implications of these facts are discussed. A more suitable mathematical model is derived from the transformed data from which it is possible to predict performance for sensation ratios other than those tested. Some possible applications of the findings to the study of driver behaviour, and their relevance to speeding offences and accident rate at the ends of motorways, are given.