Experimental measurements of perceptual thresholds in car-following. Paper prepared for the 52nd Annual Meeting of the Highway Research Board HRB, Washington, D.C., January 1973.

Experiments were carried out to measure perceptual thresholds of drivers in car-following. The results indicate that: (1) the dominant cue used to judge the sign of relative motion is the average value of relative speed divided by spacing, (2) there is response bias in favor of indicating negative rather than positive relative motion, and (3) there is a high level of sensitivity to relative motion.