Adding noise to quiet electric and hybrid vehicels: An electric issue

It has been suggested that hybrid and all-electric automobiles are so quiet at low speed in electric drive that they constitute a safety hazard for pedestrians and bicyclists. This trait has been especially troubling to vision-impaired people who rely on sound cues to avoid approaching vehicles. Assumptions have been made linking the quietness of such vehicles with fatalities and serious injuries. The U.S. Pedestrian Safety Enhancement Act of 2010, requires the use of Audible Vehicle Alerting Systems (AVAS) in hybrid and all electric vehicles. Rules are now being developed and are expected to be issued by January 2014. Similar regulations are on being promulgated in Japan and the European Union. The UN/ECE is developing a Global Technical Regulation after extensive preparatory work. SAE International and ISO are developing a method of measuring the lowest accepted noise level for vehicles. This article first notes firm evidence that the noise difference between electric-driven and ICE1 vehicles exists only at speeds below about 20 km/h (13 mph); also that AVAS makes vehicles traveling at low speeds detectable from a longer distance, absent masking background noise. Some electric and hybrid cars on the market already have AVAS installed. The author explores the assumptions related to the problem in regard to traffic safety and the harmful effects of noise on humans. One statistical study from the United States seems to suggest that vehicles driven in electric mode cause relatively more accidents involving pedestrians than do ICE vehicles. However, multiple studies in the U.S., Japan and Europe leave this causal relationship unconfirmed. Statistics about fatalities in vehicle/pedestrian collisions suggest that, at speeds where electric-driven vehicles give lower noise than ICE vehicles, the relative fatality risk is very close to zero and the risk of light or serious injuries is <5%. The author then shows that quiet vehicles, very hard to hear when approaching at low speeds, existed in urban traffic already many years before hybrid cars became common, and if quietness would create accidents this should have been apparent already earlier and not be something occurring only when hybrid cars entered the market. A number of non-acoustical ways to alert pedestrians, not the least blind people, of quiet vehicles near them are discussed and suggested in the article. The article describes the intensive work to explore the problem as well as to develop and specify AVAS systems that has been made from 2008 until now. The most recent activities are reviewed. The author argues that the work to avoid really quiet vehicles has received an incredible interest and support and has been conducted at “racing” speeds; quite opposite to the attempts made to reduce the noise of vehicles. He also argues that it would be more beneficial to human health and safety to reduce the maximum noise of vehicles rather than increasing the minimum noise of them. Consequently, the article ends with the recommendation to discontinue the work with AVAS, to limit rather than require the use of such systems, and instead focus on limitation of the worst masking noise emissions in urban areas