Abstract
In addition to a description of a methodology for obtaining information pertaining to simultaneous events is naturelistically occurring traffic, correlation al indices are used to measure the influence, both individually and jointly, of variables such as speed, relative speed, and headway upon acceleration behaviour. Major conclusions are: The most influential stimulus was the speed of the lead vehicle; (2) Time and distance head ways had essentially equivalent affects; and (3) Distance headway divided by relative speed, found to be important by others in controlled experimental settings, played only a minor role. The generally low level of driver responsiveness to the stimuli under study was such as to indicate great room for improvement.