Navigant Research Blog

EVs: Too Quiet for Comfort?

Ryan Citron — March 4, 2014

Originally thought to be one of the great benefits of electric cars, silent engines have become a major safety concern for governments around the world.  While the general population should be expected to look both ways before crossing the street, a legitimate risk is posed to blind people, not to mention children.  Electric vehicles (EVs) are mainly silent at speeds of less than 18 mph, when tire and wind noise is insignificant.  It is in this range that the U.S. Department of Transportation’s National Highway Traffic Safety Administration (NHTSA) is seeking to impose mandatory minimum sound standards for hybrids and EVs.  The standards would require automakers to produce detectable noises on these vehicles when traveling under 18 mph.  NHTSA offers recommended sound options for EVs, which are mostly modified internal combustion engine (ICE) vehicle sounds.  Although the proposals were made in early 2013, NHTSA has yet to formalize any mandatory noise-making regulations.

The Auto Alliance, which represents 12 automakers, has been openly critical of the proposed federal rules, arguing that the sound requirements should be cut off at 12.4 mph and that the costs of adding sound features have been vastly understated by the NHTSA.  The National Federation of the Blind has been highly supportive of the proposed regulations.

Sound Effects

Instead of waiting for binding legislation, some automakers have developed EV noises on their own as a safety feature.  Daimler, the parent company of Mercedes-Benz, is adding artificial sounds to its EVs.  For the company’s e-Smart city car, a “sonorous purring” has been added.  More powerful vehicles, like the Mercedes SLS AMG Coupe Electric Drive, receive huskier tones to show their muscle.  The electric smart’s sound comes standard in the United States and Japan, and is an option in Europe.  European automaker Renault offers a choice of several car tones on the ZOE hatchback – pure, glam, and sport.

What was once thought to be a competitive advantage for EVs has transformed into a contentious issue.  Although little evidence exists that the silence of EVs is a contributing factor in accidents, automakers should take the recent actions of regulatory agencies seriously, as sound standards for EVs could be instituted in the not-so-distant future.  Furthermore, sounds options for EVs present a potential market opportunity.  As discussed in a previous Navigant Research blog, EV sounds could eventually become a multimillion-dollar market consisting of ringtone-style car sounds.

One Response to “EVs: Too Quiet for Comfort?”

  1. John V says:

    Ryan: They’re NOT engines! They’re motors. Ahem.

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