And so it goes with the panic over texting while driving. I'm not going to defend the act of clumsily thumbing out an E-mail while guiding a 2-ton, gasoline-loaded missile down the highway at 70 miles per hour. That's foolish. Nor will I argue there's some right to drive while iPhone-ing tucked into a constitutional penumbra. I will argue that we need to get over the idea that we can solve every bad habit with a new law. We can't, and this issue illustrates why.

Let's start with the alleged problem. Obviously, we have more people texting behind the wheel today than we did in, say, 1985. And undeniably, those people pose a threat. But it's hard to find definitive empirical support for the idea that our highways are awash in BlackBerry-spilled blood. Since 1995, there's been an eightfold increase in cellphone subscribers in the United States, and we've increased the number of minutes spent on cellphones by a factor of 58.

What's happened to traffic fatalities in that time? They've dropped—slightly, but they've dropped. Overall reported accidents since 1997 have dropped, too, from 6.7 million to 6 million. Proponents of a ban on cellphones say those numbers should have dropped more. "We've spent billions on air bags, antilock brakes, better steering, safer cars and roads, but the number of fatalities has remained constant," safety researcher David Strayer told the New York Times in July. "Our return on investment for those billions is zero. And that's because we're using devices in our cars."

Strayer would have a point if he were looking at the right statistics. But we drive a lot more than we did in 1995. Deaths in proportion to passenger miles are a far better indicator of road safety than overall fatalities. In 1995, there were 1.72 deaths for every 100 million miles traveled. By 2007, the figure had dropped to 1.36, a 21 percent decline. That's hardly remaining constant. But let's assume that even those numbers would be lower were it not for texting drivers. It's still far from clear that banning texting will make us safer. There are countless other driver distractions that we'd never think of banning, from having kids in the back seat, to eating or drinking while driving, to fumbling with the radio. Certainly, it's foolish to type out text messages behind the wheel, but what about merely reading from your phone?

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We've seen similar nonsense on display with the general use of cellphones while driving. Though several states have passed bans, all make exceptions for hands-free devices. But we know the level of impairment of drivers using hands-free devices is essentially the same as that of drivers holding a phone. These laws aren't about safety; they're about symbolism.