The Surprising Risks of Playing It Safe


Deaths! Injuries! People are hurt every day. This is unacceptable, isn't it? We should do something about it. And when people want something to be done, they usually say that "there ought to be a law."

And so we get more laws meant to make us safer. Because 700 Americans die in bike accidents every year -- that's two a day -- lots of places now have passed laws requiring every biker to wear a helmet. It seems only sensible, since head injuries are what kill people. Public service announcements tells us that "a properly fitted helmet cushions the blow, protecting the head and brain from injury."

So helmets should protect people … like me. For years I've ridden my bike to work, and for years I rode without a helmet. It was probably very dangerous. "20/20's" offices are in New York City, which means I had to weave in and out of traffic, hoping I didn't get hit by a car. This year, I finally started wearing a helmet. I wasn't forced to, New York has no law requiring adults to wear them, but my friends talked me into it, and frankly, I was surprised to discover that today's helmets are better; they're actually comfortable.

But does my helmet make me safer? Maybe not, because safety measures often have unintended consequences.

Putting the Theory to the Test

Ian Walker is an avid cyclist and a human behavior researcher at the University of Bath in England. He set up a bike with an ultrasonic distance sensor and camera, and rode for miles with and without a helmet. His data showed that cars reacted differently when he had the helmet on.

"When I wore a helmet, there was a quite considerable tendency for drivers to get closer," Walker said.

What's the reasoning, I wondered? Is it because a driver thinks, "Oh, that rider has a helmet. … If I hit him, he'll live?"

No," Walker said. "It's that they're saying, 'He knows what he's doing.' When they see a cyclist who has all the gear, they think it's a sign of someone who's experienced and skillful."

Walker found that 23 percent more cars came within three feet of him when he wore a helmet. And, he says, there's another unintended consequence of helmet laws: fewer cyclists.

"Parts of Australia, Canada and New Zealand have made bicycle helmets a requirement. What you see is that when you make them a requirement, the number of head injuries among cyclists in those countries drops off," he said.

That sounds great, right? Fewer head injuries is a good thing. Well, not so fast.

"The number of cyclists is dropping off at exactly the same rate." Walker said.

Assuming these former cyclists don't rush out and start doing other exercise, that's not a good thing.

"When people don't cycle, they're not getting exercise," he said. "We know that not getting exercise and being sedentary is incredibly dangerous. You get heart attacks, you get strokes … proven killers that kill thousands of people. So when people make helmets a requirement, with the best intentions, it may actually kill more people."

The 'Lulling Effect'

And here's another unintended consequence. Now that I wear a helmet, I feel safer. So I've noticed that I take more risks. I ride in traffic more often. Economists call this the "Peltzman Effect:" the idea that people adjust their behavior in a way that counteracts the intended safety effect.

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