The National Highway Traffic Safety Administration is working to develop a new standard for an alert sound for hybrid and electric vehicles. As required by the Pedestrian Safety Enhancement Act of 2010, the systems will require that quiet vehicles like hybrids and electric emit a warning tone to help alert pedestrians to their approach.
NHTSA plans to solicit comments from the public, automakers, and advocacy groups for pedestrians and the blind. The Pedestrian Safety Act, signed into law on January 4, 2011, is designed to help reduce the risks of pedestrians being struck by hybrid or electric cars that are very quiet at low speeds. NHTSA has 18 months to determine things like required sounds, which vehicles must emit the noises, and other regulations. You can listen to some of the potential alert sounds at NHTSA’s website.
Electric or hybrid cars are almost silent at low speeds because their electric motors are much quieter than traditional internal-combustion engines. Pedestrians, and especially the blind, could be unaware of an approaching vehicle because they cannot hear it. Requiring an automatic alert sound would help avoid this problem. At higher speed, electric and hybrid cars produce enough tire and wind noise that a sound generator is unnecessary.
The Nissan Leaf electric car already features a sound generator, which produces a space ship-like noise when driving at low speeds, though the system can be disabled via a button on the dashboard. The Chevrolet Volt does not have an automatic alert system, but flashing the headlights at low speeds activates a brief horn honk to warn others.