Influence of Ambient Sound Fluctuations on the Crossing Decisions of Pedestrians who Are Visually Impaired: Implications for Setting a Minimum Sound Level for Quiet Vehicles

Abstract

Introduction Following the passage of the Pedestrian Safety Enhancement Act in the United States, the National Highway Traffic Safety Administration is setting a minimum sound level for hybrid and battery electric vehicles. With an aim to aid this effort, the present study investigated the timing and performance of critical street-crossing decisions by pedestrians who are visually impaired (that is, those who are blind or have low vision) at selected intersections. Methods Fourteen visually impaired adults with typical hearing along with a sighted experimenter made street-crossing decisions by indicating when they would initiate crossing using radio controller handsets. Participants’ decisions were compared with the sighted experimenter's decisions to determine the level of their risk. Results At the residential intersection, the percentage of risky crossing decisions by participants was significantly lower when the decisions were made at lower ambient sound levels (M = 8.9%, SD = 6.9%) than when they were made at higher ambient sound levels (M = 35.3%, SD = 21.2%), p < .001. The participants were able to make significantly fewer risky crossing decisions during the windows of time when the ambient sound level was lower at the major-and-minor-street intersection as well ( p = .001). Discussion Participants were often able to take advantage of the troughs in ambient sound for making street-crossing decisions, and the decisions made in lower ambient sound level conditions were generally less risky than those made in higher ambient sound level conditions. Implications for practitioners Given the finding that the level of ambient sound detected when participants made crossing decisions was much lower than the average ambient sound level at a given intersection, as long as there are noticeable dips in ambient sound, average ambient sound level at a given intersection may not be the most relevant measure of background sound level when determining a minimum sound level for the hybrid and electric vehicles.