(CNN) -- Maybe you're better off taking the bus.
A new study in the July issue of the Journal of Studies on Alcohol and Drugs found that 35% of designated drivers - those responsible for driving friends who may have had too much to drink - also consume alcohol and 1 in 5 had blood-alcohol levels high enough to impair their driving.
Researchers interviewed and tested 1,100 people in the downtown area of an unnamed Southeastern college community. Of the designated drivers who drank alcohol, half had blood alcohol levels higher than .05%, the new recommended limit for drunken driving (the current limit is .08%).
"If you look at how people choose their designated drivers, oftentimes they're chosen by who is least drunk or who has successfully driven intoxicated in the past," says Adam Barry, an assistant professor of health education and behavior at the University of Florida. "That's disconcerting."
Investigators talked to patrons as they left bars between 10 p.m. and 2:30 a.m. over six consecutive Friday nights before home football games in the fall of 2011. The average age of those interviewed was 28.
After the initial interview, which included questions about their alcohol-related behavior and their personal data, (age, gender, etc,) each person had their blood alcohol level tested.
Those who were not designated drivers had much higher levels than those appointed to drive, but 35% of the 165 self-identified designated drivers interviewed had been drinking. Most shocking to researchers was that 17% of those drivers tested had blood-alcohol levels between .02 and .049%, while 18% were at .05 percent or higher.
Perhaps, researchers say, many people don't believe one or two drinks can impair their driving. That's not true, says Barry. "That's the insidious nature of alcohol --- when you feel buzzed, you're drunk."
Mothers Against Drunk Driving (MADD) believes designated drivers are one of the best ways to keep people safe.
"MADD supports using sober designated drivers, public transportation, safe ride programs, or other means of traveling safely after drinking alcohol for individuals 21 and older," said MADD spokeswoman Carol Ronis.
However, Ronis says the designated driver needs to know that he or she cannot drink alcohol.
The National Transportation Safety Board last month recommended all 50 states adopt a blood-alcohol content cutoff of 0.05 compared with the 0.08 standard used today to prosecute drunken driving. If states will act on this recommendation still has to be seen. According to Barry, the American Medical Association made the same recommendation in the 1980s, but the recommendation was never considered.