How Drunk Is Too Drunk to Drive?

Our podcast “The Suicide Paradox” featured sociologist David Phillips, who spoke about his research on copycat suicides (a phenomenon he calls “the Werther Effect”). More recently, Philips has been studying drunk driving. Particularly, he’s been looking at drivers who are merely “buzzed” — with 0.01 percent blood alcohol concentrations (BACs) — and has found that the severity of life-threatening motor vehicle accidents increases significantly at BACs far lower than the current U.S. limit of 0.08 percent. In an email, Philips describes his latest research on buzzed drivers:

My current research, just published in Injury Prevention, shows that even minimally buzzed drivers (with BAC=0.01%) are 46% more likely to be blamed for an accident than are the sober drivers they collide with. This indicates that there is no safe level of alcohol for drivers: any amount of alcohol markedly increases the risk to drivers and their passengers. We reached this conclusion after examining an official, U.S. dataset of more than 570,000 car crashes. The findings have implications for drivers, passengers, police, judges, lawyers, insurance companies, advocacy organizations (like MADD) and regulatory agencies.

The paper, “Official blame for drivers with very low blood alcohol content: there is no safe combination of drinking and driving” (abstract; PDF), is co-authored with Ana Luiza Sousa and Rebecca Moshfegh. The researchers used an official nationwide U.S. database (Fatality Analysis Reporting System) for the years 1994–2011. They found that there’s “no sudden transition from blameless to blamed drivers at BAC=0.08% (the U.S. legal limit). Instead, sole official blame increases smoothly and strongly with BAC (r=0.98 (0.96–0.99) for male drivers, p<0.000001; r=0.99 (0.97–0.99) for female drivers, p<0.000001). This near-linear SOB-to-BAC relationship begins at BAC=0.01% and ends around BAC=0.24%.”

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  1. Matt says:

    “Official blame” is not the same thing as actual responsibility for a crash.

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    • Jamie says:

      The causal link between drinking and recieving “offical blame” may not be impairment. It could well be a bias held by reporting officers against people who admit to drinking before getting behind the wheel – a bias which is shown in the presumptive title of the study itself!

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    • Jon says:

      It seems pretty obvious that the fact or admission that one driver had alcohol in his or her system would bias conclusions reached by the police or insurance companies. Justifiably or not.

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    • EJ Campbell says:

      Hidden due to low comment rating. Click here to see.

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      • JimFive says:

        It does matter. If BAC is blamed for more accidents then the legal limit will be lowered to reflect the perceived risk. That lowered level would cause more people to be officially drunk driving even though they are not significantly impaired. It can lead to people drinking more and driving because it doesn’t matter since they’ll be driving illegally no matter how much they had to drink.

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  2. TedS says:

    It’s a good point that impairment increases continuously as BAC increases, but it doesn’t follow that we should punish those at .01% BAC. Many other physical/psychological states impair driving (tiredness from lack of sleep, fatigue from a long day at work, stress or anger from a fight with a spouse, distraction from a conversation with a passenger) yet we make no attempt to quantify the impairment of such states. We probably should quantify the impairment if only for the sake of comparison.

    I suspect that (a) blame tends to go to a driver with non-zero BAC by default, and (b) the increase in risk from being at low BAC levels (as opposed to zero) is smaller than the factors mentioned above, which we ignore. If we are going to pass new driving laws, we should be targeting the biggest risk factors. I doubt low BAC drivers are very high on the list considering many states still have weak or absent cell phone driving laws.

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  3. Walter says:

    Hidden due to low comment rating. Click here to see.

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  4. Jonathan says:

    This sounds like a classic case of reverse causality. The police only breathalyze people who they think are at fault…

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  5. Phil Persinger says:

    It’s both amusing and illuminating to be in an Australian city when the bars close and to see all the revelers and bar-flies pour themselves into taxis for the ride home. Cars are retrieved the next day after coffee.

    The max legal BAC in Oz is .05% and drivers are admonished that impairment begins at lower levels

    .. and this in the land of Foster’s, XXXX beer and Bundaberg rum.

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    • Sam K says:

      Does taking a taxi home from the bar actually save lives? At a minimum you have 3 times as many miles driven and on two legs you have twice as many people in the car. Add in the danger from the taxis driving around looking for a fare and the benefit of driving the “buzzed” home is negligible (or negative).

      But it makes us feel good, right?

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      • Phil Persinger says:


        Maybe you’re right. I’m sure that Australia doesn’t have hard figures on your question and aren’t likely to care since Australians sure like to feel good. Maybe you could get a grant to do a study; you might be their only hope.

        Nevertheless, .05% is the law there (and in many other countries) and has been for many years. If there were a problem as great as you hypothesize, some tweaking would have been done by now and the cab business would have been suppressed. Oz is a democracy, after all…

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      • Sam K says:

        There’s absolutely no question that driving buzzed (or even drunk) is sometimes safer than other legal and socially approved options (I gave only one of many examples). It’s often unclear what we should do with such results, but that is no reason for us not to study and try to understand them.

        I do not share your faith that if there were a problem that it would have been identified and fixed by now, there are too many examples to disprove that (e.g. the drunk walking study). Especially when emotions are involved and the safety of children is used as a club to silence any possible dissenting views.

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      • Phil Persinger says:


        Well, that’s public policy for you: not always evidence-based. Sadly.

        Good public policy can’t be developed– even though it often is– from something’s (driving drunk, buzzed or slightly loopy) being hypothetically superior because it’s “sometimes safer” than alternative means of transport (taxis, designated drivers, etc.). If everyone exercised proper judgment in all cases, we wouldn’t need laws. There’s a point beyond which the exercise of individual freedom becomes a public menace. You and I clearly differ in this case on where that point lies.

        I think you’re not going to find a lot of evidence against maintaining or lowering BAC standards. Many posters here have pounded the Phillips, et al., article; if you actually read the thing (and it ain’t an easy read) you’ll see that the authors seem to have addressed many, if not all, of the issues brought up in this forum. Since the it was published by a peer-reviewed journal (under the aegis of the British Medical Journal), I imagine that readers there– more knowledgeable than we– will point out any weaknesses in the article’s methodology and conclusions. Stay tuned.

        You are absolutely correct, however, that emotion or sentiment is bad basis for public policy.

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      • Sam K says:

        Phil, we aren’t talking about relying on people to do the right thing in all cases, far from it. We are talking about using the right metrics and giving people the right incentives to do the right thing. If the law (and social standards) often encourages people to do the “wrong thing” then that is clearly a problem, isn’t it?

        Simply eliminating or lowering the BAC limit is clearly not the solution, that kind of black and white thinking is part of the problem. Likewise, just because I don’t think our current TSA policies are effective and necessary doesn’t mean I think we should allow anyone to bring a handgun onto an airplane. To paraphrase your statement: there is a point at which blind obedience to an inefficient law is a public menace.

        Let’s just be honest about the topic first and see where it goes from there.

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      • Phil Persinger says:


        Thank you for your reply.

        I agree that blind obedience to “bad” law can result in public menace, but how exactly are DWI laws any more inefficient– or less necessary– than other laws affecting public conduct? (Post-9/11 security laws, like WWII internment camps, represent a special case and should be dealt with in a separate discussion.)

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      • Sam K says:

        Are we only supposed to tackle the problem that is the most serious (dangerous, inefficient, …) at any one time? If that is your philosophy then you should find 99% of Freakonomics to be unworthy and uninteresting.

        I’ve pointed out one example of how DUI laws (and the ways they are enforced legally and socially) cause actions that are not only not in the best interests of the individual, but not in the interest of society. I can point out many others, but if you were honest with yourself on the topic you should be able to identify them without my help.

        Finding a better and safer solution may only save a few thousand lives, but I think it’s at least worth thinking about. Won’t anyone think of the children?

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      • Phil Persinger says:


        Thank you for your post.

        I apologize for not doing a good job laying out my thoughts. My last post merely asked how in your opinion DWI laws diverge from sound public policy.

        To what example of yours do you refer? The one about the danger of a taxi’s being more dangerous than a buzzed (or drunken) driver because it’s traveling three times (at a minimum) as far with twice the occupants? Is that an example extracted from a data-based study or is it a scenario for how things might go wrong? I don’t know how many bars or nightclubs you’ve “closed down” in your life, but more than a few of the departing clientele are not pretty sights. I’d lay my public policy with the cabbies. Just sayin’.

        What would be your better and safer solution to DWI?

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      • Sam K says:

        Yes, Phil, that is the example I was referring to and you continuing to not grasp it is indicative of how many either intentionally or because of emotion refuse to be honest about drinking and driving.

        What data would you suggest that I provide to demonstrate that 3 is greater than 1 (or that 5 is greater than 1)? To move the conversation along I think we should just accept those as given.

        Your observation about closing down bars is also a distraction that is so often brought up to muddle the conversation. The fact that there are many stumbling drunks who are a certain hazard on the road is irrelevant to the cases that we’re talking about. Once again, we don’t have to choose between our current laws and just allowing any level of intoxication and dangerous driving. I am not advocating that drunks should NEVER take taxis, but I really shouldn’t have to say that (again).

        The optimal laws and enforcement would of course be different depending on many factors including the congestion, public transport options, weather, time of day, etc. Driving is inherently dangerous and every driver has different capabilities and different ability to drive while drinking, talking on a phone, or changing the radio station. Not to mention that some cars are much safer than others.

        So if the goal is to have a minimum number of accidents then all factors should be taken into consideration, shouldn’t they? Even if it’s not practical to implement such laws in detail we should at least be able to discuss it honestly, which you seem very reluctant to do.

        One idea for a better approach would be just stricter enforcement of every traffic rule. Poor or dangerous driving should be punished no matter the cause. Someone who drives 30 miles to a nice restaurant and doesn’t drink is quite probably more of a risk than the guy who drives a mile to a bar and has 3 drinks and that should be considered. If we really care about safety and aren’t just looking to persecute, that is.

        I apologize if my post is a little obnoxious, but it really doesn’t seem like you’re trying very hard to understand the points I’m making.

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  6. KevinH says:

    My guess is that this research will increase the % of buzzed drivers that are blamed for a crash.

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  7. James Halliday says:

    I’ve always been interested in the effects of ageing on the ability to drive.
    Some countries seem to be slowly pushing for mandatory re-tests/examination, but until that point there seems to be an assumption that you’re absolutely fine.
    Alcohol is always (and rightly) something that’s focussed on as a deliberate, self-inflicted, impairment to your ability to drive safely – but there are so many other factors that are completely ignored.
    Another one might be eye-sight. Surely it makes sense that if you’re driving you’ve done your best to optimize/correct your vision – but I’m unaware of any attempt to enforce mandatory eye-testing and wearing of resultant corrective devices, before you’re designated a ‘safe driver’.
    Would be interesting to get access to insurance companies raw data. Theoretically, you start as a teenager as a ‘high risk’ and your premiums (adjusting for speeding tickets, DUI convictions, car cost, estimated mileage etc) should decrease. If we could track where this didn’t happen, it would be fascinating to know why.

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    • Enter your name... says:

      Having slightly imperfect vision might not increase accidents, so true optimization is probably not necessary. Also, it’s more complicated than that: what if laser vision correction makes mine better than yours during the day, but a little worse than yours at night? Do we ban you from driving during the day because yours isn’t “optimized”?

      Every single time I’ve gotten a driver’s license, I’ve had to take a vision test. I don’t know about other countries, but in the US, eye-testing and wearing any necessary corrective lenses is required. It’s marked on the driver’s license, so it’s easy to enforce.

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    • JimFive says:

      Re: eyesight
      I don’t know where you are but we have vision tests in order to get and renew our licenses. My license says “Restrictions: Corrective Lens”

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  8. Mike says:

    I’ll keep piling on. How does an officer find someone with .01% BAC? By suspecting the person of being drunk. Someone who appears drunk at even .01% BAC is probably more likely to be a bad driver in general. Drivers who don’t appear drunk at .01% BAC aren’t going to get tested at all. So the .01% crowd here isn’t going to be representative of all drivers with .01% BAC.

    I suspect that all this study has shown is that bad drivers sometimes also have a non-zero BAC.

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    • Chris says:

      Good point. Also, were they tested for anything else? You might have .01% BAC and a much higher percent of some other drug.

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