What makes a driver drunk ?

4. Drunk Driver Data Don’t Walk Straight Line Either

Rarely Do Intoxicated Motorists Get Caught, and When They Do, the Meaning of Blood-Alcohol Levels Is Hazy

June 10, 2009

What makes a drunken driver really drunk?

That question was highlighted by Mothers Against Drunk Driving’s decision Monday to remove a liquor-industry-funded group from a high-profile campaign to prevent drinkers from taking the wheel. The group, called the Century Council, argues on its Web site that hard-core drunken drivers cause most alcohol-related traffic deaths, and therefore any crackdown should focus on them.

But there is a big question about that approach: How do you identify really drunken drivers before it is too late? Drunken drivers are rarely nabbed. When they are caught, it may be after one of their milder binges. And even if they are tested, the legal limits are somewhat imprecise — one size doesn’t fit all.

The dispute over crash statistics is complicated by the number universally used to measure drunken driving: blood alcohol content. It is rarely monitored by drivers and poorly understood even by the most sober minds. Despite this confusion and the fuzziness of test results, penalties for drunken driving tend to be more black-and-white than for speeding fines, which increase as speed does.

MADD split with the Century Council because the two groups disagreed about a penalty requiring drivers caught above the limit to install an ignition interlock, a device that prevents those convicted from driving whenever their breath alcohol is too high. The liquor-backed group told several states it only supported this measure for the most hard-core drivers. These include repeat-offenders and people whose blood alcohol content exceeds 0.15 grams per deciliter of blood — a much higher level of alcohol content than the legal limit of 0.08.

The basis for the Century Council’s hard-core threshold comes from government tests of drivers involved in alcohol-related fatal crashes in 2007, showing three out of five had a BAC of at least 0.15.

Other research establishes that these heavy drinkers are far more dangerous than other drunken drivers on the road. Paul Zador, a statistician at the research company Westat, has compared the blood-alcohol levels of drivers killed in crashes with levels of drivers stopped for random roadside testing during peak drunken-driving hours. That helped him estimate how likely it is that an extra drink will prove fatal. Compared with sober drivers, drivers at 0.15 or higher were about 400 times more likely to die in a crash. Drivers with levels between 0.10 and 0.14 were 50 times more likely than sober drivers to die in a crash.

These troubling rates, cited by the Century Council in its campaign against hard-core drunken drivers, might overstate the role of alcohol in killing heavy drinkers. As Dr. Zador notes, the same personality traits that lead to driving while highly intoxicated are probably tied to other risky behavior behind the wheel. These drivers are likely dangerous even before they have had their first sip.

And drawing the line legally at 0.15 assumes that it is a magic number identifying habitual drunken drivers. Researchers estimate that there is just one drunken-driving arrest for every 80 to 300 trips taken by drunken drivers. The Century Council itself says that there are 1,000 to 2,000 drunken trips per arrest in low-enforcement zones. A Centers for Disease Control and Prevention study published this month found that passengers report 290 million annual episodes of impaired driving, or 200 for every arrest.

On that one trip where a habitual drunken driver is stopped or killed, his blood-alcohol content might be below 0.15 even if it has often been higher. In a 2002 study co-authored by Susan Baker, a professor at Johns Hopkins University’s Bloomberg School of Health, researchers drew upon an intriguing data source: interviews with surviving family members of 818 victims of fatal crashes.

The next of kin painted a frightening portrait of those dead drivers with a BAC of 0.15 or higher: 55% were described as drinking and driving at least once a month. But those whose blood-alcohol level was between 0.10 and 0.14 — and thus mostly wouldn’t have qualified as hard-core — weren’t much safer: 35% drove drunk at least monthly. “We shouldn’t simply be focusing on ‘hard-core’ drivers,” Prof. Baker says.

Still, the Century Council is sticking to the 0.15 threshold. “We think the decision to drink enough to get to 0.15 or above is a dramatically dangerous decision,” says Ralph Blackman, chief executive of the group.

Even blood-alcohol levels of 0.05 impair motor skills and heighten crash risk, and many countries draw the line there or at 0.02. MADD isn’t pushing for a reduction. “We have no intention of going below 0.08,” says Chuck Hurley, chief executive of the group. “We want 0.08 enforced.” He says aggressive enforcement and penalties, particularly ignition interlock, would save more lives than an effort to lower the limit, which would “take us five years and we would accomplish nothing else.”

Because impairment starts with the first drink, at least for some drivers, and increases gradually, some researchers would prefer to see a lower limit, with penalties tied to the blood-alcohol level, like with speeding penalties. “There isn’t a magical point at which your speed makes you a dangerous driver,” says David Hanson, a sociologist at the State University of New York, Potsdam.

To prevent speeding, you can keep track with a speedometer. But cars aren’t currently equipped with alcohol testers. Without a number on the dashboard, drivers rely on their own math skills. That may be a good thing, since drinkers tend to overstate how drunk they are. One study of 152 undergraduate students during prime drinking hours found that their own hazy memories of their night of drinking overestimated their blood-alcohol levels by about one-third.

Complicating matters, people’s alcohol-metabolism varies, as does the relationship between their breath alcohol — which is what is usually measured — and their blood alcohol. That has been a favorite line of argument for some defense attorneys. In response, some jurisdictions have based their laws directly on breath-alcohol levels, according to Rankine Forrester, chief executive of Intoximeters Inc., which makes breath-alcohol testers. That solves the legal gray area but creates a scientific one, because intoxication arises from blood alcohol, not breath alcohol.

In a decade, drivers, hard-core and otherwise, may have alcohol testers built into their cars. Mr. Hurley, of MADD, is encouraged by a joint effort between the Department of Transportation and auto manufacturers to develop built-in alcohol-detection systems in cars that would prevent their operation when drivers are above the alcohol limit. If the systems work, MADD would support their installation in new cars. The system could also tell drivers what their level is. Says Mr. Hurley: “We wouldn’t want people to use that to always get up to 0.079 and think they’re OK.”

WSWA is leveraging member visits with Congress to also voice concern with the potential unnecessary and duplicative regulatory burden that would be imposed by the inclusion of beverage alcohol in legislation designed to overhaul regulations governing the nation’s food supply.  As an integral part of the three tier system, wholesalers have set the gold standard for efficiently – and safely – bringing a diverse selection of beverage alcohol products to the consumer marketplace for generations.

Like many prominent national trade associations, WSWA’s annual Legislative Fly-in provides an opportunity for representatives from member companies to visit Capitol Hill to meet with their representatives and key congressional leaders to discuss issues that affect and impact their businesses.

For more information about WSWA and its views on the issues, visit www.WSWA.org.