On July 7, 2011, the National Highway Traffic Safety Administration (NHTSA) announced it would begin studying the environmental impact of requiring "quiet" hybrid and electric vehicles to emit sounds alerting pedestrians of their presence at low speeds. The study is the first step in a process that will result in a formal rulemaking requiring vehicle manufacturers to install sound emitting technology on all new hybrid and electric vehicles, including passenger cars, motorcycles, trucks, and buses.

NHTSA is commencing its study in response to mandates included in the Pedestrian Safety Enhancement Act of 2010 (PSEA), which requires the agency to determine the types of sounds that would be most effective in alerting pedestrians to quiet vehicles and what impact these sounds would have on community noise levels. PSEA requires NHTSA to issue a new motor vehicle safety standard for hybrid and electric vehicles through a rulemaking once it has made these determinations. It also requires NHTSA to consult with vehicle manufacturers as it develops the standard. Under the law, NHTSA must issue a notice of proposed rulemaking (NPRM) by July 4, 2012, and a final rule by January 4, 2014. Once the final rule is issued, vehicle manufacturers will have up to three years to phase-in sound alert technology.

Congress passed PSEA because it was concerned that hybrid and electric vehicles pose a unique safety risk to the visually impaired and other pedestrians since they operate much quieter than internal combustion engine (ICE) vehicles, particularly at low speeds near street crossings. This concern was highlighted in a study issued by NHTSA in 2009, which concluded that the rate of accidents involving pedestrians was higher with hybrid vehicles than will non-hybrid vehicles. A follow up report, issued in 2010, found that electric and hybrid vehicles emitted less sound than ICE’s and could impact pedestrian response times.

Since PSEA passed in December, 2010, NHTSA has been laying the groundwork for its rulemaking on quiet cars. It cited the rule as a priority in its 2011-2013 Vehicle Safety and Fuel Economy Rulemaking and Research Priority Plan, which was issued in March, and is now preparing for the 2012 NPRM by commencing the environmental study. Public comments may be submitted during each phase of the rulemaking process, including the study.

A detailed summary of NHTSA’s proposed environmental study and rulemaking can be found here.