The increase in availability of alternative fuel vehicles has elicited concerns for pedestrians who might not hear the approach of these quieter cars. Three experiments tested the relative audibility of hybrid vehicles (in their electric mode) and internal combustion engine (ICE) cars. Binaural recordings were made of the cars approaching from either the right or left, at 5 mph. Subjects were asked to listen to these recordings over headphones and press one of two buttons indicating from which direction the car approached. Subjects’ accuracies and reaction times were measured. The first experiment revealed that (sighted) subjects were able to determine the approach direction of the ICE cars substantially sooner than the hybrid cars. A second experiment added the natural background sounds of idling engines to the stimuli. The addition of background sound disproportionately hindered perception of the hybrid cars, so that they could not be localized until very close. A final experiment testing both sets of stimuli with blind subjects revealed the same pattern of results. Implications of these results for pedestrian safety will be discussed. [Work supported by a grant from the National Federation for the Blind.] (Author/publisher)
Abstract