A study of 1,071 bar-goers shows that many designated drivers drink and end up impaired behind the wheel.

It turns out that many designated drivers believe it’s their job to drink less than their friends but not to abstain from alcohol completely.

A study released Monday by researchers at the University of Florida found that as many as 40 percent of designated drivers consume alcohol, many to the point where their driving may be affected.

The study, published in the Journal of Studies on Alcohol and Drugs, assessed the blood-alcohol concentration (BAC) of 1,071 people during six anonymous field studies in college bar districts the night before home football games. Of those people, 165 said they were the designated drivers for the night.

Forty percent of the designated drivers reported drinking and 17 percent had BACs of 0.02 to 0.05. An alarming 18 percent had BACs of 0.05 or higher. The majority of impaired designated drivers (DD) were below the legal definition of intoxication, which is a BAC of 0.08 or higher.

In all 50 states, the legal blood alcohol limit for drivers is 0.08, but the National Transportation Safety Board (NTSB) recommends that states lower the limit to 0.05.

“The research clearly shows that drivers with a BAC above 0.05 are impaired and at a significantly greater risk of being involved in a crash where someone is killed or injured,” NTSB Chairman Deborah A.P. Hersman said in a press release last month.

Lead researcher Adam Barry, an assistant professor of health education and behavior at the University of Florida, warned that a person’s driving skills can be impaired even before a “buzzed” driver realizes he or she has had too much.

“People do try to use that as a measuring stick, but alcohol is insidious,” Barry said in a press release. “If you’re going to be a designated driver, you should abstain from alcohol use completely.”

Besides the challenge of controlling a car while “buzzed,” Barry cautions that other distractions are likely with a car full of drunk friends.

“They may be loud, or start roughhousing. They’re a distraction,” he said.

“Considering the low BAC levels at which driving-related abilities are negatively affected, these findings identify the need for consensus across researcher, layperson, and communication campaigns that a DD must be someone who abstains from drinking entirely,” the researchers concluded.