The relative contributions of distance and speed are compared in order to explain the variance of real and estimated times in a time to arrival experiment. Thirty subjects, classified by sex and three levels of driving experience, (non-drivers, beginners and experienced), replicate, with different speed values, the experiment of Recarte, Nunes and Lillo (1993) in which an automobile test and a laboratory test were performed. In the automobile the subjects, travelling as passengers, estimate in conditions of visual occlusion, the time of arrival at a target. Sixteen different times are generated, varying orthogonally the distance of visual occlusion, (150, 125, 100, 75m before the targets) and the speed (70, 90, 110, 130km/h). In the laboratory test the subjects estimated the time of arrival of a mobile with a horizontal trajectory on a computer screen. The general analysis confirms the same effects found in the previous experiment, in particular, the general tendency to underestimate, the paradoxical effect of driving experience, the internal consistency of both tasks and the absence of correlation between them. Both experiments (the present one and that previously cited) were compared, analysing the logarithms of the real and estimated times, as a function of the logarithms of speed and distance. When considering the relative contributions of speed and distance, speed explains in the estimated times a higher proportion of the accounted variance than in the real times. The same times generated by different speed and distance combinations are not equivalent. Variations in real times produce different effects on the estimations depending on whether they are produced by changes in distance or changes in speed.
Abstract