Designated drivers in one Florida college town are having a hard time avoiding the bottle, with two out of five drinking before taking the road. Nearly half of these inebriated motorists had a blood alcohol content (BAC) of .05 percent, which is enough to impair driving ability, even though it is under the legal limit. The findings were reported today in the Journal of Studies on Alcohol and Drugs.

Alcohol-impaired drivers are involved in about 1 in 3 car fatalities, resulting in nearly 11,000 deaths per year. To curb these accidents, many states have launched public awareness campaigns to promote the practice of designated driving.

But do designated drivers always stay sober? Many studies suggest designated driving advertisements aren't reducing the number drunk drivers on the road.

Social pressure in combination with a legal BAC limit of .08 percent means a person could have a few drinks and drive without committing a crime. However, scientists argue that a single drink can alter driving coordination.

"The vast majority of studies document significant alcohol-related impairment at a BAC level of 50 mg/dl (.05 percent)," write the authors led by Dr. Adam Berry, assistant professor of health education and behavior at the University of Florida, Gainesville.

To assess how many designated drivers partake in libations before getting behind the wheel, a group of University of Florida researchers spent three months surveying over 1,000 bar patrons as they were leaving ale houses in the college town of Gainesville, Fla. The team asked individuals if they were a designated driver and to volunteer for a breathalyzer test.

Of the 165 self-identified designated drivers, 35 percent had at least one drink before taking the road. About half had a BAC between .02 and .05 percent, which is enough to alter some aspects of driving awareness, while the rest were above .05.

The subjects were predominately male (62 percent), although women accounted for one-third of the non-abstaining designated drivers.

The authors point out that it might be especially dangerous for designated drivers to imbibe alcohol given it is likely they will have drunk passengers.

"They may be loud, or start roughhousing. They're a distraction," said Barry. "Couple all of that with the fact that most people drink at night, when any driver's vision is diminished, and you have a potential recipe for disaster."

On a positive note, the majority of self-reported designated drivers did completely abstain from alcohol.

This analysis was conducted in a college town with a preeminent football program; thus, the results presented in the study may not broadly apply to drinking culture across the country. Similar investigations in other communities are needed.

Based on this one study, it is impossible to tell if alcohol use is a rising or falling trend among designated drivers in this area. A long-term study that mirrors the design of this one, perhaps that circumscribes the introduction of anti-drunk driving campaign, could resolve some of the debate as to whether PSAs actually impact the drinking habits of designated drivers.

Source: Barry AE, Chaney BH, Stellefson ML. Breath alcohol concentrations of designated drivers. Journal of Studies on Alcohol and Drugs. 2013.