The risk of a silent accident is greatest when EVs are traveling at low speeds. Above 18 mph or so, the sound generated by tires and wind is loud enough for passersby to recognize the danger.

Many EVs, including the Chevy Volt and Toyota Prius, can already emit warning noises, but they are not yet legally required. Regulators have thus far focused on setting a required decibel range for EVs traveling below that 18 mph threshold. But that may not be the most effective approach. “For different types of sounds at the same pressure level [an objective measure of sound strength], audibility is very different,” Pedersen told Quartz. Varying frequency or differentiating from ambient noise can make a sound more noticeable, even at lower decibel levels.

Until regulators and and car companies find a comprehensive solution, be extra-careful when jaywalking.

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