Drinking and driving – how much is too much?

Last week, the media was full of stories of the carnage on our roads over Easter and the growing chorus of calls to cut the blood alcohol limit to tackle drunk drivers. MacDoctor is sceptical a cut – from the current limit of 80mg/100ml to 50mg/100ml, will make any difference.

But scientists in an SMC briefing we held last week said the evidence suggests a cut that would put New Zealand in line with many other countries at the .05 level would result in less crashes, less road deaths and less cost to the state as a result.

But what would a cut mean for the average male and female wanting to drive home after a couple of hours drinking after work? How much less will be need to drink to stay legal if the law changes? With the help of ESR and graphic designer Zef Zugaz, we created an infographic to show visually just what the change will mean…

SMC infographic on blood alcohol limits
SMC infographic on blood alcohol limits

Here’s how The Press redesigned our image for their front page story:

The Press: Traffic lights are go
The Press: Traffic lights are go

And here’s the New Zealand Herald’s take, which ran on page 2:

Blood alcohol - Herald Infographic - April 9, 2010
Blood alcohol - Herald Infographic - April 9, 2010

So which infographic works best?


  1. Grant Jacobs

    I think you may be missing what I was saying. I wasn’t trying to say one kind of campaign is better than another; I just pointing out the infographics aren’t aimed at the more fundamental issue and the people I know think more about the effect than what the legal limit happens to be (but in the context of reasoning that the legal limit is higher that the level that is asking for trouble for most people).

    a lot of people will still cause accidents because they are going to get drunk and drive anyway or they are high on drugs as well, but at least you can educate the average drinker on how much they can consume before safely getting behind the wheel.

    I agree, it was part of what I was trying to get at although there is more (obviously!).

  2. Peter Griffin

    Grant, I think the failure of 15 years of road safety ads suggests the message about crash risk isn’t getting through. I don’t think a graphic in a paper is therefore going to make a difference. As MacDoctor points out, a lot of people will still cause accidents because they are going to get drunk and drive anyway or they are high on drugs as well, but at least you can educate the average drinker on how much they can consume before safely getting behind the wheel. That will be vitally important if the BAC does actually decrease, which is looking increasingly likely.

  3. Grant Jacobs


    Is there a survey of what “most people” think?

    Seriously, I’m sceptical 🙂 Happy sceptic smiley… 😉

    Most people I know are more interested in they’re safe to drive home or not, i.e. how much can they drink before they’re likely to be danger to themselves (or others, but reality is people tend to think about themselves too and generally first…) It’s common knowledge that the “getting caught” level is over the “can cause danger” level (for many/most people), which is part of why I and others I know think that way.

    Personally, I’m not content with letting the papers sell the “wrong” issue 🙂 I’m not being naive, btw, people do think in terms of “getting caught” of course, as my final sentence was meant to indicate. It’s hard to remember now, but I probably did as a kid. It makes me think there is an element of needing to think about who thinks what and try get people to think in terms of safety, not “will I get caught”. (Who as in what age group, etc.)

  4. Peter Griffin

    Repton he also says this: “The problem is actually not the amount of alcohol in your blood stream, but the degree of impairment when you drive”. And this “It is also doubtful that any movement of the BAC limit, even to zero, will make any difference to the kind of people who get behind the wheel of a car with a BAC 0f 0.18%.”

    Which I think is why he is proposing some type of “fit to drive” test rather than a reduction in the BAC

  5. Repton

    You misread MacDoctor’s post. He’s not at all skeptical that it will make a difference. Quoting: “There is plenty of evidence that lowering the legal Blood Alcohol Concentration (BAC) reduces accident rates, injuries and fatalities in an almost linear fashion.”

    MacDoctor’s point is that reducing the threshold to 0.05 will reduce accidents. Reducing it to 0.06 will reduce accidents, but by a bit less. Reducing it to 0.03 will reduce accidents by more. So why do we pick 0.05? (or why 0.08, for that matter?)

    There’s a discussion to be had about what we gain from drinking and driving, compared with what it costs us. But we’re not having that discussion.

  6. Peter Griffin

    Grant, the crash risk may be the key big picture issue, but I think for a graphic going in a newspaper, most people are interested in how many beers they can drink and safely and legally drink home – and how this might change with a lowering of the blood alcohol limit.

  7. Grant Jacobs

    I prefer the Herald ‘Crash risk’ side bar to all the others.

    Several reasons:

    – it took me quite a while work out *precisely* what the horizontal scale in the first two is and it’s not completely clear still. I prefer well-marked axis. My initially reading of the first was that the 6th dot was “one standard drink”! Looking at the Press on, I see *each* dot is one standard drink. Very different. My initial reading of the If the first chart left me wondering if the first dot meant zero or 1/6th of a standard drink (which, in turn, determines what the marked transitions mean. While the first is clearer in the sense of less cluttered and presented nicely, you *must* define the horizontal axis clearly. The line to the sixth dot is *quite* misleading. I actually couldn’t make sense of it until I read the Press “give-away” “one dot = 1 standard drink”.

    – the main part of the Herald presentation is confusing, doesn’t add more than the numbers they give anyway and doesn’t clearly relate to the drink-driving test (The relationship of the 50 vs. 80mg/l levels to testing might have been given in the article, but graphs should stand on their own.) The first does this well, but! —

    – with the exception of the ‘crash rate’ sidebar none of these relate to the crash risk, which is the key issue at hand (although I would have preferred it compared to any kind of crash, as opposed to only fatal crashes). What the others don’t relate to are the *effects*, which is the issue at hand. (To be correct they relate to one effect “would I get caught”, which I’m sure bothers many people, but it’s not the fundamental issue.)

  8. Peter Griffin

    Thanks Brent, my concern about the Herald one is that it could be interpreted as meaning you can, as a male, drink up to 9.3 drinks in the third hour, on top of the other drinks – which would be up to 22 drinks in three hours! It is cumulative, so you can actually drink 5.6 – 9.3 drinks OVER THREE HOURS.

  9. Brent Jackson

    The one you designed is easily the clearest. The herald one is extremely unclear, although the Crash Risk graph at the side is interesting. I loathe the way some graphic designers make things look pretty but obscure the information that they are trying to display (eg three dimensional-looking bar graphs). The New Scientist went through a phase of doing this a few years back, but seem to have gotten over it.


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