Designated drivers volunteer to be the responsible ones for the night, dutifully sipping club soda for a few hours and then safely ferrying their silly, wasted friends back home from the bar.
But a new study finds that about 40 percent of designated drivers drink - and almost 20 percent of all designated drivers drink enough to significantly impair their ability to drive.
This news should be unsettling, even shocking, and to many people it must be. But to those of us familiar with the young (and not so young) adult bar scene ... yeah, that sounds about right.
Too often, sometime around last call in far too many bars across the country, a cringe-worthy survey of sorts is done among drinking buddies: Who here is "least drunk"? The winner ("winner") is awarded the keys, and named the night's designated driver.
"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," says Adam Barry, lead author of the new study published today in the Journal of Studies on Alcohol and Drugs.
Barry points out that even in the academic literature, there isn't really an agreed-upon definition of "designated driver" - is it a person who abstains from alcohol entirely, or who maybe has a drink or two but stays under the legal limit for driving?
This paper, at least, suggests that many DDs believe their role fits the latter definition. To figure this out, researchers from the University of Florida interviewed about 1,000 people exiting bars in a southeastern college town; of those interviewed, 165 said they were serving as DD for their friends that night.
The researchers spent about five minutes asking questions to drivers and non-drivers, and then gave the interviewees a Breathalyzer test (the same equipment a police officer would use).
They found that around 40 percent of designated drivers had had at least a little something to drink. And 17 percent of all the designated drivers had breath alcohol concentrations (BrACs) between .02 and .05, and 18 percent had BrACs of .05 percent or more.
"I recognize the levels we have in our article is not .08," the blood-alcohol content limit for legal driving in all 50 states, Barry says. But for most individuals, by the time they reach a .02 BAC, "driving tasks such as divided attention are impacted. Once you hit .05, that's basically when the vast majority of the literature says you are significantly impaired."
Just last month, the National Transportation Safety Board recommended lowering the legal blood-alcohol content level for driving to .05. To put it into a global context, the United States' current legal limit of .08 is on the higher end.
Countries across Europe like Germany, France and Italy have a limit of .05; in Sweden, Norway and the Netherlands, among other places, it's .02; and many countries have zero tolerance laws.
Think about all the things a designated driver has to be alert and sharp-minded enough to endure: besides the actual driving of the car, there are pedestrians, cyclists and other vehicles to contend with outside the car -- and then inside the car, you've got your drunken friends bouncing around, messing with the radio, whining for Taco Bell.
And this isn't just a college kid issue - about 40 percent of the drivers in this study were not students, and their average age was 28. Also, as the ages of the drivers in this study went up, so did the BrAC levels, Barry says.
The big question now, of course, is how on earth to change people's behavior. "What I would suggest is prior to ever going out, make a plan. Decide who's going to be the designated driver, and make sure that person does not drink. And I understand people go out, plans change, people buy you drinks without you asking -- but if those plans change, it's time to look to public transportation."
Or a cab! Or an on-demand car service like Uber, if your city has one and you're feeling fancy! Both of which can be expensive, but are ultimately cheaper and safer than the consequences of a DUI or, so much worse, a crash.