Hybrid Cars Are So Quiet They’re a Menace to Pedestrians

Reviews of cars, trucks, and other autos.
May 15 2012 7:07 AM

The Silent Killer

Hybrids are so quiet that pedestrians never hear them coming. Now automakers are racing to make the car of the future sound like the gas guzzlers of old.

A Toyota Prius car.
The quiet engine of hybrid and electric cars at low speeds poses a risk to pedestrians

Jed Leicester/Getty Images.

Forget gas mileage: The most striking aspect of the new Ford Focus Electric is what it doesn't have. "Battery-powered cars are intrinsically quiet, the motor sound falling between a whir and a whisper," marvels a New York Times review of the car. "But the Focus is deep-space silent, the quietest of the many electric cars I’ve driven."

And that, it turns out, is a problem. Thanks to the Pedestrian Safety Act of 2010, by this summer the National Highway Traffic and Safety Administration is required to initiate a rulemaking process for minimal vehicle noise—not how quiet, but how loud a car must be. That's because NHTSA studies in 2009 (pdf) and 2011 (pdf) confirmed what many long suspected: Hybrids and electric cars are too quiet for the blind or even the fully sighted to hear them coming. Though the NHTSA found little statistically significant difference in collisions over 35 mph—when wind and tire noise negate the difference in engine noise—at lower speeds, hybrids and electric vehicles are 37 percent more likely to hit walkers and 66 percent more likely to collide with cyclists than traditional gas-powered cars.

The victims didn't hear it coming—but did automakers? As counterintuitive as adding car noise may seem, we've long had comparable safety laws in place: For instance, we add foul-smelling Butanethiol to natural gas so that it doesn't sneak up on us in our homes. But there's an even more apt comparison: sleigh bells. Back in the age of real horsepower, the jingling of bells had little to do with winter cheer, and plenty to do with not getting trampled to death. As early as 1797, Baltimore slapped one-dollar fines on anyone who didn't make their sleighs noisy enough. Other cities followed suit, and even the future Motor City had a tough sleigh-bell ordinance that could land silent sleigh drivers in jail.

Advertisement

The problem that electric cars posed was apparent from the dawn of the motor industry, when primitive gas and electric vehicles were already battling for primacy. As early as 1900, journalist Cleveland Moffett was hailing the electric car as "the automobile of the future"—a status it has held ever since—in no small part due to it being "free from noise." A contemporary electric car guidebook noted that construction had already advanced to the point where noise was "scarcely perceptible." But by 1908, an electric car guide warns "with the silent electric car, especial care is needed to avoid running down incautious pedestrians." After the death of a pedestrian that same year, one EV driver was moved to write to the Commercial Motor magazine with the question that has haunted the industry ever since: "Is Some Noise Desirable?":

I would like to raise the question as to the expediency of noiselessly running motor vehicles. Not that I wish to commend the present terrible clatter of some of them; but, so much having been made of this quality of noiselessness by the electric-vehicle people in particular, I will so far as to assert that the worship of noiselessness will result in motor vehicles becoming too quiet.

In the absence of much regulation, automakers responded with ... well, bells. Newspaper columnist Frederick Othman marveled at driving a Rauch-Lang Electric Brougham through St. Louis in 1916: "you went silently like a panther. ... [A pearl button] caused a tinkle, like a peculiarly melodious doorbell. The car was so quiet that it was inclined to sneak up on pedestrians, and scare 'em. So there was a good deal of tinkling."

Though electric cars were to disappear under a sea of petroleum for the next 60 years, even a brief resurgence of interest in 1964 spurred the Long Beach Press-Telegram to note that pedestrians would soon need "agility and good peripheral vision." When the oil shocks of the 1970s hit, the renewed interest in EVs quickly revealed the problem again, with one 1979 Department of Energy report generating nationwide headlines of "Electric Cars Too Quiet?"