"The Pedestrian Safety Enhancement Act of 2010 was approved by the U.S. Senate by unanimous consent on December 9, 2010 and passed by the House of Representatives by 379 to 30 on December 16, 2010.The act does not stipulate a specific speed for the simulated noise but requires the U.S. Department of Transportation to study and establish a motor vehicle safety standard that would set requirements for an alert sound that allows blind and other pedestrians to reasonably detect a nearby electric or hybrid vehicle, and the ruling must be finalized within eighteen months. The bill was signed into law by President Barack Obama on January 4, 2011.
A proposed rule was published for comment by the National Highway Traffic Safety Administration (NHTSA) in January, 2013. It would require hybrids and electric vehicles traveling at less than 18.6 miles per hour (30 km/h) to emit warning sounds that pedestrians must be able to hear over background noises. The agency selected 30 km/h as the limit because according to NHTSA measurements, this is the speed at which the sound levels of the hybrid and electric vehicles approximated the sound levels produced by similar internal combustion vehicles.[30][31] According to the NHTSA proposal, carmakers would be able to pick the sounds the vehicles make from a range of choices, and similar vehicles would have to make the same sounds. The rules were scheduled to go into effect in September 2014. The NHTSA estimates that the new warning noises would prevent 2,800 pedestrian and cyclist injuries during the life of each model year electric and hybrid vehicle.[31][32]
In February 2013, the Association of Global Automakers and the Alliance of Automobile Manufacturers, which submitted a joint comment to the NHTSA, announced their support to the rule, but asked the NHTSA to find a noise level that effectively alerts pedestrians without being excessively loud to others inside and outside of the vehicle. They also commented that the rule is too complicated, unnecessarily prescriptive, and it will cost more than necessary. Some automakers also said there is no need for electric-drive vehicles to play sounds while not in motion, "since it is not clear that it helps pedestrians to hear cars that are stopped in traffic or parked." In addition, the carmakers requested the NHTSA to make the new sound system required by 2018 instead of 2014.[31][33][34]
In January 2015, the NHTSA rescheduled the date for a final ruling to the end of 2015. Since the regulation comes into force three years after being rendered as a final rule, compliance was delayed to 2018.[35] In November 2015, the NHTSA rescheduled one more time because additional coordination is necessary. A final ruling was delayed at least until mid-March 2016."
