Public Health

Hybrid Cars' Silence Just One Factor In High Pedestrian Death Rate

Cars and pedestrians. i

Hybrid vehicles are twice as likely to kill pedestrians as their conventional cousins, but why? iStockphoto.com hide caption

itoggle caption iStockphoto.com
Cars and pedestrians.

Hybrid vehicles are twice as likely to kill pedestrians as their conventional cousins, but why?

iStockphoto.com


Hybrid cars and SUVs —which switch to silent, battery power when gliding or braking or standing still — are about twice as likely to kill pedestrians as their full-throated counterparts are.

But the deaths may not have been due to the silence.

That's what Amy Freeland, an investigator with the Centers for Disease Control and Prevention, found out when she analyzed data in the files of the National Highway Transportation Safety Administration from more than 200,000 traffic-related fatalities from 2004 to 2008.

Most of the fatal encounters occurred when the hybrids were going faster than 35 mph — when they're making the same amount of noise as a conventional vehicle.

"There's a piece we don't know about this," says Freeland. "And I think that may be market distribution." She suspects — but can't yet prove — that people who drive in crowded areas with high pedestrian traffic, like cities or beach towns, are more likely to drive hybrids. More pedestrians means more chances of a pedestrian accident.

One of the charming but disconcerting things about hybrids is the way the engine cuts off when the car stops using gas. That leads unaccustomed drives to fear the engine's suddenly died.

But it's dangerous for those outside the car, too. Without that engine thrum, blind people, distracted pedestrians, and folks listening to music (or, OK, the radio) may not know a car is close by. And that's worried safety advocates for years.

This new study doesn't exonerate silence, though. It dealt only with fatalities. It's possible that hybrids bear a disproportionate responsibility for non-fatal injuries, too.

Legislation in Congress to deal with silent cars seems to have stalled out. There's discussion at the car companies about adding sounds to hybrids.

At the meeting where Freeland presented her data, someone in the audience said one of the companies was considering a frog sound — but that couldn't be confirmed.

In the meantime, Freeland suggests everyone try and drive a little safer.

Freeland presented her study at the annual meeting of the CDC's Epidemiology Intelligence Service. These are the famed disease-hunters who try to figure out what's sickening and killing people — not the sort of group normally discussing transportation stats.

But Freeland took a personal interest. During her previous career as a therapist for the blind, Freeland wanted to know whether hybrids are any more dangerous than other vehicles for them. She says a lot more study is needed to see what's really going on.

Freeland herself does not drive a hybrid. She bought her car in 1999, before they were widely marketed in the U.S. She's considering a hybrid next time around, though.

"Hybrids are great," she says. "They do wonderful things for the environment."

Just watch out if you are a pedestrian.

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