STUDY: About 40 Percent Of ‘Designated Drivers’ End Up Having At Least One Drink

Designated drivers — the people who volunteer to stay sober so they can safely drive others home from bars or parties — aren’t necessarily following through on their promise to refrain from drinking, according to a new study published in the Journal of Studies on Alcohol and Drugs. About 40 percent of designated drivers end up having at least one drink, and nearly 20 percent drink enough to impair their ability to drive.

“There’s evidence that says designated drivers often times are chosen because they’re least intoxicated — or they’re chosen because they’ve successfully driven a car intoxicated previously,” Adam Barry, the study’s lead author, told NBC News.

That may reflect some confusion around what it means to volunteer as the designated driver in the first place. Some people might assume that person is signing up to abstain from drinking entirely, while others may view it as someone who has a few drinks but remains under the legal limit for driving. Barry explained that even when it comes to academic literature, there’s no consistent definition for “designated driver.”

The researchers point out that this isn’t just an issue among college kids. Forty percent of the drivers who participated in this study weren’t students — and older designated drivers were actually more likely to have more alcohol in their systems. As the ages of the study’s participants went up, so did their blood alcohol levels.

The current legal limit for driver’s blood alcohol content (BAC) in the United States is 0.08. Barry explained to NBC News that, although many of the designated drivers in his study were technically under that limit, that doesn’t mean they weren’t impaired. Most people’s ability to drive is impacted by the time they reach a 0.02 BAC. “Once you hit .05, that’s basically when the vast majority of the literature says you are significantly impaired,” Barry explained.

That’s why the National Transportation Safety Board (NTSB) recently recommended that the U.S. should drop its legal BAC limit down to 0.05. That change would bring the United States in line with the more than 100 countries that have already adopted laws forbidding an alcohol content of more than 0.05. Alcohol-related crashes kill about 10,000 Americans each year, and the federal board estimates that tightening the standards for drunk driving could save an annual 500 to 800 lives.