Electric Car

The Sound of Silence

A spokesperson for Fisker says the Karma, its electric sports car due out next year, will warn pedestrians by emitting a noise possibly “akin to a jet fighter.”

By 2020, one in every five cars sold in the U.S. will be a hybrid electric vehicle. That’s nice for the planet, but bad for pedestrians who can’t hear the quiet vehicles’ approach. Some automakers will equip hybrids with artificial engine sounds, but some drivers say that less noise pollution isn’t such a bad thing. Here, a cheat sheet to the noisemaker debate.

To Vroom

Experiments by psychologist Lawrence Rosenblum of the University of California at Riverside found that subjects listening to recordings of combustion-engine vehicles approaching at 5 mph—with traffic noise mixed in to simulate a parking lot—could detect its familiar rumble at a distance of 28 feet. They couldn’t detect a Toyota Prius going that speed until it was just seven feet away. The work was funded by the National Federation of the Blind, but Rosenblum says quiet cars also pose a risk to small children, the elderly, cyclists and runners.

Pending approval in Congress, the Pedestrian Safety Act would require the National Highway Traffic Safety Administration to study the minimum decibel level required to alert the blind and other pedestrians to motor vehicles, including high-end gas-powered cars. If the act is passed, the Secretary of Transportation must set a new standard within 90 days of the study’s completion, to go into effect two years later.

Not to Vroom

Traffic noise is excessive in many urban areas, and some studies suggest that long-term exposure to the din may make people more susceptible to health problems, including hearing impairment and heart attack. Cars are less dangerous at low speeds, and hybrids are silent only below 20 mph—above that, tire and air friction create enough noise to make even all-electric cars audible. The U.S. Department of Transportation has not found any evidence that hybrid cars are associated with increased accidents involving pedestrians.

A better way to protect pedestrians, some hybrid drivers suggest, is to require collision-avoidance systems or front-end airbags on all cars, although these are more complex and expensive than noisemakers. If hybrids must emit sounds, some argue, consumers should be allowed to customize them like cellphone ringtones. The company Better Place, which is developing networks for recharging electric vehicles, has already copyrighted the term “drivetones.”

So what do you think?

Should electric vehicles be equipped with a noise-making device for safety?(trends)