Drinking and driving is serious business. Last week, the National Transportation Safety Board (NTSB) recommended that states lower the current blood alcohol concentration limit of 0.08 percent to 0.05 percent or lower.
“We continue to kill 10,000 people annually in these crashes (involving alcohol), injuring 173,000, and 27,000 of those injuries are debilitating, life-altering injuries,” says NTSB chairman Deborah Hersman. Lowering the legal driving BAC limit was one of 19 recommendations released in a NTSB report titled “Reaching Zero: Actions to Eliminate Alcohol-Impaired Driving.”
Experts say it’s tough to provide a number of drinks per hour that would set you above the legal limit of 0.08 (or the suggested limit of 0.05) because there are just so many factors that go into how your drinking affects your body. The strength of the drink (a strong beer versus a light one, for example), whether or not you have food in your stomach, how quickly you’re going through drinks, and your weight all come into play, says Alexander C. Wagenaar, PhD, professor of health outcomes and policy at the University of Florida College of Medicine.
Another big factor is serving size; think about the heavy pours you get at certain restaurants, and check out this infographic to see how the serving sizes of different drinks compare.
Alcohol can also affect women differently than men: When you drink alcohol, the ethanol diffuses into all the water-soluble parts of the body, explains Wagenaar, who has been doing research on road safety and alcohol issues since the early 1980s. In general, women naturally have a higher percentage of fat tissue than men—which means less water-based tissue for the ethanol to diffuse into. So even if a woman and a man of the same weight consume the same amount of alcohol, the woman will end up with a slightly higher BAC.
Under normal circumstances, if you’re 200 pounds, it’s unlikely that you’ll hit the proposed 0.05 limit after two drinks—”but that assumes some time passes between the drinks,” says Wagenaar. “If you weigh 90 pounds, at the other extreme, well then it’s possible—and not at all unlikely—that one drink on an empty stomach could hit a woman to the (proposed) 0.05 limit,” he adds.
For a 140-pound woman, one drink would probably put her around the 0.03 BAC level, says Wagenaar.
Those are all rough estimates, of course; since you probably don’t carry a breathalyzer around in your clutch, there’s really no way to know exactly how a drink will affect you on any given night.
In its recent report, the NTSB cited research showing that by 0.05 BAC, most people experience visual and cognitive impairments. The report also notes that more than 100 other countries—including the majority of European countries—have a BAC limit of 0.05 or lower. “The risk is very definitely there, and it’s not insignificant at 0.05,” says Wagenaar. “That’s why 0.05 is a logical legal standard that’s in place in most developed countries in the world.”
At 0.05 BAC, people are 38 percent more likely to be in a crash than people who are completely sober, according to research cited in the NTSB report. At 0.08 BAC, people are 169 percent more likely to be in a crash than people who haven’t had anything to drink.
Here’s the deal, though: Regardless of whether the legal BAC limit is set at 0.08 or 0.05, the fact remains that even a little bit of alcohol does affect your ability to drive safely. “When you need to cognitively attend to more than one thing at a time—which is a clear part of driving—those types of abilities begin to deteriorate even at the low levels of drinking,” says Wagenaar. “So the safest is to not drink and drive at all—I mean zero BAC.”
If you’re planning to drink, have a designated driver with you, or take a cab home (save taxi numbers in your phone beforehand!). There are even apps and websites out there for connecting you with a designated driver that will get you and your car home safely, like StearClear and this National Directory of Designated Driver Services.
The verdict: A glass of wine or a beer over a long dinner probably won’t put you over the proposed legal limit of 0.05 BAC—depending on your weight, how big/strong the drink is, and other factors. But of course the safest personal policy is not getting behind the wheel after any drinks. And if you educate yourself now about the resources available to get you home safely, you should be able to avoid driving yourself there—even if you end up drinking when you hadn’t planned on it.
More from Women’s Health:
Don’t Mix THIS with Alcohol
This Is Your Brain on Booze
Is Your Drinking Habit Deadly?