Whenever someone is hurt in an accident, people say, "There ought to be a law!" Politicians rush to oblige them and then take credit for all the lives they saved.

But shouldn't they also accept blame for the lives lost because of those laws?

Lives lost? Yes. A joint study by the Brookings Institution and American Enterprise Institute [http://www.aei-brookings.org/publications/abstract.php?pid=98] found that government regulations that are supposed to save lives actually end up killing more people.

Why? Because safety laws almost always have unintended bad consequences.

For years I've ridden my bike to work without a helmet, which seemed especially dumb since "20/20"'s offices are in New York City. I feel much safer now, but it's not clear that I am safer.

Ian Walker, a human-behavior researcher at the University of Bath in England, put a sensor and camera on his bike and rode for miles with and without a helmet. His data showed that when he wore the helmet, 23 percent more cars came within three feet of him.

"[The drivers are] 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 surmises.

Biking is obviously less safe if cars are closer. Walker says there's another unintended consequence of helmet laws.

"Parts of Australia, Canada, and New Zealand have made bicycle helmets a requirement. The number of head injuries among cyclists in those countries drops off."

That's good, right?

"However, the number of cyclists is dropping off at exactly the same rate."

That's not good, assuming they don't take up other exercise.

"When people don't cycle, they're not getting exercise," Walker says. "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." Continued...