A new study found that even though participants knew drunk driving was dangerous while sober, their convictions weakened once they became intoxicated.

THURSDAY, September 12, 2013  Public health initiatives have long warned of the dangers of drinking and driving, but the approach of teaching people to avoid drunk driving while they’re sober may be futile, according to new research published in Alcoholism: Clinical & Experimental Research. This is because by the time people are making choices about drunk driving, they’re drunk, and according to the study, the drunkenness interferes with their perception of the danger and their ability to drive.

Researchers from the University of Missouri asked 82 young adults aged 21 to 29 to participate in two sessions, one in which they remained sober, and another in which they consumed enough alcohol to put their blood alcohol contents (BAC) above the legal limit to drive (0.08).  During each session, the researchers asked the participants about how dangerous they thought driving while drunk is. They also asked about their willingness to drive at various points as they became more intoxicated and eventually sobered up. When the participants were sober, they were asked about the dangers of driving for a hypothetical BAC.

The researchers found that the facts the participants proved they knew while sober were often severely diminished after the participant had been drinking. Basically, not only are drunk individuals too impaired to drive, they’re often also too impaired to make the decision not to drive, even if they know drunk driving is dangerous. This means they may still make the choice to drive while drunk, an action that’s responsible for nearly one-third of all fatal car crashes annually in the United States.

“It’s unlikely at the height of the moment when one is about to drive that past education will come into play and be recalled, particularly because of the clear impairment in judgment,” said Daniel Ehlke, assistant professor of health policy and management at SUNY Downstate Medical Center School of Public Health.

Not only this, but researchers assessed willingness to drive both as individuals became more intoxicated by continuously drinking (called ascending), and then as their BACs decreased after they stopped drinking (called descending). Individuals who were on their way to becoming sober were more willing to drive than they had been while continuously imbibing, even though their BACs were identical in each case.

“People tend to think they’re less impaired at the same point on the descending limb vs. the ascending limb,” said study author Denis McCarthy, associate professor at the University of Missouri. “When they’re on the descending limb, some things are starting to come back, but your sense of how intoxicated you are recovers faster than a lot of your motor skills."

The study is limited in the fact that “when you do a laboratory study, you can’t get people as drunk as they would get on their own,” McCarthy said. While people may be drinking more in the real world, the levels of intoxication reached in the lab may really reflect the most dangerous drunk drivers, said Elkhe. When people become visibly intoxicated, they’ll either realize they can’t drive, or people around them will force them not to drive. However, when people have drunk moderate amounts of alcohol, they may not seem impaired and may be more willing to get behind the wheel even when they shouldn’t. “Buzzed driving is drunk driving,” said Elkhe, quoting a recent TV ad he saw on the matter, adding that he was encouraged by the ad.

Beyond public awareness campaigns, which people often hear when sober, reminders not to drive that are seen while people are drinking could be useful, McCarthy said, citing a recent attempt to have urinal cakes, objects that sit in the bottom of a urinal, programmed to launch a recording encouraging people not to drunk drive each time the urinal is used.

“The urinal cake idea is kind of weird, but that kind of creativity is the next thing we need to be doing,” McCarthy said. Other effective options include breathalyzers to start and drive a car, though those are only used after someone is caught, and more randomized roadside checks.

Being sure to make specific plans for transportation when people are going to be drinking is particularly important, said Elkhe, and once those plans are set, it’s critical to stick to them.

The study only included younger adults, who may be more likely to take the risk to drive while intoxicated. “There’s a reason why the insurance industry calls 20-somethings the young invisibles,” Elkhe said. Drunk driving rates tend to decrease in older people, though the older individuals who are still drunk driving are often harder drinkers and repeat offenders, he noted.