New electric car regulation could replace the hum of a near-silent EV motor with an artificial buzz, in the hope that fewer pedestrians will be killed or injured from not realizing cars are around them. Proposals from the National Highway Traffic Safety Administration (NHTSA) for minimum sound requirements for electric vehicles could save up to 2,800 pedestrian and cyclist injuries over each model year, the US organization estimates, though the sound itself would be up to manufacturers to decide upon.
"The sounds would need to be detectable under a wide range of street noises and other ambient background sounds when the vehicle is traveling under 18 miles per hour" the NHTSA says of the proposed legislation. "At 18 miles per hour and above, vehicles make sufficient noise to allow pedestrians and bicyclists to detect them without added sound."
The agency even has a page of suggested sounds, as well as some of the reduced-level road noise which it's concerned about. One key element is Doppler shift, for the distinctive change in tone depending on where a moving vehicle is in comparison to a person, and whether it's ahead or behind them. Although most people don't realize they're doing it, Doppler is used to automatically process whereabouts a moving vehicle is in relation to them.
"Each automaker would have a significant range of choices about the sounds it chooses for its vehicles, but the characteristics of those sounds would need to meet certain minimum requirements" the NHTSA said. "In addition, each vehicle of the same make and model would need to emit the same sound or set of sounds."
Some manufacturers are already working on custom sounds for EVs. Audi, for instance, cooked up a special "e-sound" which is dynamically adjusted according to driving style, speed, and other factors, much in the same way that a traditional engine changes.
"Federal Motor Vehicle Safety Standard No. 141" will be submitted to the Federal Register for public comment this week, with a sixty day period for feedback. The potential standard is another example of how automotive technology is butting heads with legislators and safety demands; last year, the NHTSA proposed driver distraction rules that could threaten complex in-car touchscreen dashboards, such as those which feature in Tesla cars.
Update: We asked Tesla for an official comment on the proposed rules. "As regulations are put in place, Tesla will work to be in compliance with any laws" the company told us.