Pedestrians’ time-to-collision estimation and road crossing judgments differ between electric and conventional vehicles

Abstract

Pedestrians can only safely cross the road before an approaching vehicle if the time remaining until the vehicle arrives at their position (time-to-collision, TTC) is longer than the time needed to cross. In real traffic, the sound of a vehicle provides important information about its motion. Using a virtual reality (VR) system that combines physically plausible acoustic simulations of approaching vehicles with visual VR simulations, we investigated if the sound differences between electric (EVs) and conventional vehicles (ICEVs) result in differences in the perception and behavior of pedestrians. In this paper, we present an overview of our results. 1) When vehicles approaching with a constant velocity are presented with the same TTC, participants estimate longer TTCs for softer compared to louder vehicles both in an auditory-only and an audiovisual condition. This indicates potential risks associated with quieter vehicles. 2) When the sound of an accelerating conventional vehicle is presented, this largely removes the inadequate consideration of acceleration (first-order estimation pattern, resulting in overestimated TTCs) observed in visual-only TTC estimation. 3) For accelerating EVs with and without AVAS, the benefit provided by the car sound is significantly reduced compared to ICEVs. 4) Compatible with these TTC estimation results, the collision probability in road-crossing decisions when interacting with accelerating vehicles increases significantly with the acceleration level for EVs with and without AVAS, but remains low for ICEVs. Taken together, auditory information is relevant for pedestrians, particularly so when the approaching vehicle accelerates. Our data indicate potential risks associated with EVs, and raise interesting questions concerning the design of acoustic vehicle alerting systems.