As the adoption of hybrid and electric vehicles (HVs and EVs) increases, concerns have emerged regarding their relative quietness with respect to pedestrian detectability. Although all pedestrians face a possible increase in risk due to lower operating noise associated with HVs and EVs, the visually impaired and blind community faces an even greater potential for risk due to their reliance on hearing as an assessment for when it is safe to cross a roadway.

Vehicle manufacturers have started implementing additive noise solutions designed to increase vehicle detectability while in electric mode and/or when traveling below certain speeds. This paper presents a single effort undertaken to evaluate the United Nations Economic Commission of Europe’s (UNECE’s) proposed evaluation method for quiet road vehicles, as well as to assess performance between two additive noise approaches. This effort also evaluated detectability of an EV with no additive noise versus a traditional internal combustion engine (ICE) vehicle.

Twenty-four legally blind individuals participated in a daylong session evaluating detectability of approaching vehicles within a controlled environment. Vehicle approach scenarios consisted of two levels of steady-state speed, and a scenario where vehicles came to a complete stop. Participants, seated within one lane of a closed-test track, declared auditory detection of an oncoming vehicle by pushing a hand-held button.

Findings suggest that although mean detection distances trend higher for vehicles with an additive noise component, they aren’t significantly different from traditional EVs at speeds of 10 kph. Moreover, all EV/HVs were detected at significantly shorter distances relative to the ICE vehicle. At an approach speed of 20 kph, however, these differences become indistinguishable, likely due to the additional road noise produced by tires at higher travel speeds.

The findings from this study provide justification for the usefulness of examining additional vehicle types, approach maneuvers, road surfaces, and noise levels within the same general context. Furthermore, the findings from this study provide guidance regarding the impact of EV additive noise on detectability, particularly as it relates to the vision-impaired population.