Estimation of time to vehicle arrival--effects of age on use of available visual information

Subjects estimated time of vehicle arrival while viewing twenty-four film clips of an approaching vehicle, half with a constant viewing time of 4.2 s and half with a constant vehicle-movement distance of 40 m. The distances from the subject at which the film ended were 20, 60, and 100 m. Speeds of approach varied between 7.45 and 15.44 m s-1. Performance was strongly dependent on age of the subject. Subjects in the 5-6-year-old group made estimates based on the distance of the vehicle; at 7-8 years an interaction between the effects of distance and velocity appeared and for 9-10-year-olds there was a main effect of the vehicle velocity. Only for adults was the information from distance and velocity fully integrated. There was no significant difference between males and females for any of the age groups. Performance of adults was very similar to that reported by other authors in that subjects underestimated the time to arrival of the vehicle, with estimated times about 60% of the actual times. Standard deviations of the estimated times were such that a small percentage of subjects overestimated times and hence would have caused a collision if they had proceeded with a crossing. The mechanism of time estimation was strongly dependent on the angular velocity of the vehicle subtended at the eye of the observer. This must exceed a threshold value of about 0.002 rad s-1 (adults) if a linear relationship between estimated and actual times is to be obtained.