The perception of manoeuvres of moving vehicles. Progress Report II: Effects of lateral motion on thresholds for relative sagittal motion.

This report is concerned with the psychophysics of compound motion. The movements of the taillights of a leading vehicle moving in darkness on a course making an angle with the observer's heading direction were simulated. Subjects were required to judge whether the lights moved relative to one another, that is they had to detect a sagittal motion component in lateral motion. The independent variables were exposure time, viewing distance and lateral motion speed. The results were treated in terms of signal detection theory.