Acoustic Characteristics of Hybrid Electric Vehicles and Safety of Blind Pedestrians

Quieter cars, such as electric vehicles and hybrid electric vehicles (HEVs), may reduce auditory cues used by pedestrians to assess the state of nearby traffic and, as a result, their use may have an adverse impact on pedestrian safety. To document differences in the sound levels of HEVs and internal combustion engine (ICE) vehicles, the authors measured the sound pressure levels in one-third octave bands of three HEVs and three corresponding ICE vehicles for the following operating conditions: idle, backing up at 5 mph, approaching at a constant speed (6, 10, 20, 30, and 40 mph), accelerating from stop, and slowing from 20 to 10 mph at 3.28 ft/s². Sound level results comparing the HEVs with the ICE vehicles are presented. In general, HEVs have lower sound levels than ICE vehicles for operating conditions below 20 mph; but above 20 mph, the sound from road–tire interactions dominates and the sound levels of the two vehicle types converge.