Metro area residents have a high IQ when it comes to knowing the law about drinking and driving. More than 63 percent know that a .08 percent blood alcohol concentration (BAC) is the limit for legally operating a motor vehicle.

We know the law better than Americans in 10 other cities surveyed about alcohol awareness, the law and consumption decisions by the Foundation for Advancing Alcohol Responsibility.

But turns out we are still fuzzy about how much we can imbibe and still be OK to drive.

Before heading to that holiday party and tipping one back, belly up to the Virtual Bar, a tool the nonprofit that fights against drunken driving put on its website ( to help revelers know when to say when.

The Virtual Bar calculates your BAC based on the type of drink and your gender, height, weight, age, and whether you've eaten or had water to go with your booze. A 200-pound man at 6 foot 3 would be at a .08 BAC after consuming five glasses of wine in a one-hour session. That's too tipsy to drive.

Of course there would be no threat to anybody on the roads if somebody sober took away the inebriated person's keys, something we are loath to do. While 85 percent of respondents said they have the confidence to stop somebody who has overconsumed from getting behind the wheel, only 49 percent have actually intervened.

"They may see that as crossing a boundary or look like it's imposing," said foundation president and CEO Ralph Blackman. "There is definitely a disconnect there."

That's sad. The holidays are supposed to be a joyful time of celebration. Yet last year, 945 families mourned the deaths of loved ones killed in crashes involving a drunken driver between Thanksgiving and New Year's Eve, according to the National Highway Traffic Safety Administration.

For party hosts, keeping drunken drivers off the road has never been easier. There are many options for offering a safe ride home: ride-sharing, sober cabs, taxis and even public transportation (Metro Transit will offer free rides on buses and light-rail lines from 6 p.m. New Year's Eve until 3 a.m.). Still, 75 percent of metro area residents don't think about using alternative forms of transportation when heading out.

Mothers Against Drunk Driving launched the designated driver idea more than 30 years ago. At first, those who carted their drinking friends around were seen as the killjoy or the one left out of the fun, Blackman said.

Now, they're earning a special place in the group. "It's not the barrier it used to be," he said. With Instagram, Facebook and Snapchat, "they regale the group with all the funny things that happen during the evening. Everybody has a good time."

Designated drivers have become an important tool to promote a change to a culture where traffic deaths and serious injuries are not acceptable, says Donna Berger, director of the Minnesota Department of Public Safety's Office of Traffic Safety. Alcohol-related fatalities are down 21 percent since 2010. "That's small comfort if you've lost a loved one to a drunken driver. That's why we ask Minnesotans to 'join the crowd' and plan a sober ride," she said.

With that in mind, start a new tradition this year and be a designated driver. It may be the best gift you give somebody this season.