Acoustic Vehicle Alerting System

A class of vehicle systems that emit artificial sound to alert pedestrians and other road users to the presence and movement of quiet vehicles — typically electric and hybrid vehicles at low speeds, where tire and aerodynamic noise are insufficient for detection. Regulatory frameworks such as U.S. FMVSS 141 and UN Regulation No. 138 mandate AVAS for most new electric vehicles, typically requiring sound output below a specified speed threshold (roughly 20-30 km/h). AVAS is particularly significant for blind and low-vision pedestrians, who rely heavily on engine and tire noise to detect approaching vehicles, judge their speed and direction, and make safe crossing decisions; ineffective, optional, or defeatable AVAS directly threatens their safety.