Quieter vehicles result in riskier pedestrian street-crossing decisions

We investigated whether vehicle sound power affects pedestrians’ street-crossing decisions. In a virtual environment, we presented high-fidelity interactive acoustic and visual simulations of a vehicle approaching a pedestrian standing on the sidewalk, in an auditory-only and an audiovisual modality condition. The vehicle was presented for several seconds and then disappeared from the display and was no longer audible (hereafter referred to as “occlusion“). Participants judged whether, at the moment of occlusion, they could have safely started crossing the street the street while the vehicle was approaching (i.e., accepted the gap), or whether they had to wait until the vehicle passed them. Using an adaptive psychophysical procedure, we measured psychometric functions mapping the relationship between the arrival time of the vehicle at the moment of occlusion and the probability of a gap-acceptance decision, and introduce a novel measure of the riskiness of the individual crossing decisions. The results showed that participants accepted shorter gaps and made riskier crossing decisions when the vehicle sound power was lower compared to higher. This effect of sound power occurred in both modality conditions, though it was stronger when only auditory information was available. Reverse-correlation analyses of the trial-by-trial data showed that the vehicle sound intensity at the pedestrian’s position was the most important predictor of the decisions in the auditory-only condition, but that participants did not base their decision exclusively on the sound intensity. In the audiovisual condition, sound intensity also was significantly associated with the crossing decision, but visual cues dominated. Implications for road traffic safety are discussed, specifically concerning interactions between pedestrians and quieter electric vehicles.