As a rule, it's a bad idea to let pedophiles baby-sit, to hire embezzlers as tax collectors, or to give a pyromaniac a key to the fireworks factory. We generally try to avoid inviting dangerous people into situations that encourage them to repeat their destructive behavior. So why do we allow drunken drivers unfettered access to their cars?
That's a good question, for which New Mexico authorities had no good answer. For years, the state ranked among the worst in the nation in alcohol-related fatalities. So three years ago, it decided a change was in order.
In the past, authorities had relied on license revocations to get drunks off the road. But here's a surprise: People who ignore laws against driving drunk also tend to ignore laws requiring them to have a valid license. For some, taking away their license had all the impact of confiscating their library card.
So the legislature, prodded by Gov. Bill Richardson, imposed a tighter constraint on those convicted of DWI: requiring a device that keeps a car from being operated by someone who's been drinking. Other states have mandated ignition interlock devices for those with multiple convictions, but New Mexico was the first to order them for all first offenders upon conviction.
The results were swift and sharp. Since the law took effect, the rate of drunken driving fatalities has dropped by nearly 20 percent. Nationally, by contrast, the rate rose slightly during that time, including in Maryland.
New Mexico DWI Czar Rachel O'Connor - that's her actual job title - notes that the state's campaign against drunken driving includes other steps as well, from a massive public-service ad campaign to intensive use of sobriety checkpoints. But the interlock rule has been a major factor in the improvement.
Some 7,000 New Mexicans have to pass a breath-alcohol test before they can start their cars. Adding up all the times that motorists have failed the breath test, Ms. O'Connor says, the mandate has prevented 63,000 trips by offenders who have been hitting the bottle.
Now the state has additional evidence that its approach is working as intended. A new analysis of New Mexico's experience, published in the journal Traffic Injury Prevention, finds that first offenders were 60 percent less likely to be rearrested if they had interlock devices than if they didn't. When the gadgets were removed, their recidivism rate rose to nearly the same level as those who had never had them.
That isn't terribly surprising. People who get behind the wheel of a two-ton machine when they're under the influence tend to be people with serious alcohol problems, and they tend to keep driving drunk as long as we let them. Suspending their licenses deters some, but Mothers Against Drunk Driving says research indicates that about three out of every four keep driving anyway.
Interlocks are the obvious solution. But so far, only four states have mandated them for all first offenders upon conviction.
Even then, they're not an insuperable obstacle. Determined sots can hotwire their cars, borrow vehicles or have someone else - such as a child - blow untainted carbon dioxide into the devices. Another problem, says Ms. O'Connor, is that some offenders claim to have gotten rid of their cars, signing them over to friends or relatives but retaining surreptitious use of them.
Still, the requirement does work to prevent a lot of impaired driving. And it puts no burden on taxpayers, since offenders bear the $1,000-a-year cost.
It also has benefits for the culprits. In most states, the standard method for stopping drunken drivers is to revoke their licenses so they aren't allowed to drive at all. Under this policy, they may drive all they want as long as they're stone cold sober. It incapacitates the incorrigible while sparing the repentant. A canceled license, which lets the offender police his own conduct, does just the opposite.
In 2006, more than 14,000 people across the country died in accidents involving drunken drivers. If that number strikes you as too high, interlocks for all DWI offenders is one proven way to lower it.
Steve Chapman is a columnist for the Chicago Tribune. His column appears Mondays and Fridays in The Sun. His e-mail is firstname.lastname@example.org.