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Should We BAC Down?

Drunk driving doesn’t grab our attention like the oil slick, perhaps because the damage comes in a steady drip instead of (literally) one big gusher. But the costs we pay for the interaction between alcohol and driving are large, in terms of lives lost, medical care, property damage, enforcement, and more.
There are definitely ways we could save lives through additional policies to control DUI. But some may be more effective than others, and all would come at a cost in terms of a pleasure that many of us enjoy and even rely on. So which trade-offs might be worth making?
Here’s one possibility: cutting the legally permissible BAC from .08 to .05. James C. Fell and Robert B. Voas have done an extremely helpful study that reviews the research on this potential policy change.
The beauty of studying BAC limits is that we have lots of neat natural experiments; over the years many places have lowered permissible alcohol levels, so we can see what has happened when they did.
For example, at the start of the 1970s some states had no formal legal BAC limit, and most that did set it at .15. Eventually, most states moved to .10. Starting in 1983, states began to reduce this to .08 and since 2002 all states have been at that level.
This change has been accompanied by a precipitous drop in accidents involving alcohol: in 1982 there were 1.64 alcohol-related road fatalities per 100 million miles driven, and in 2008 there were only 0.40.
Granted, we can’t attribute all or even most of this to reduced BAC limits. Lots of different anti-drunk driving measures were taken during that time, like better education and harsher penalties. Besides, travel in general got safer thanks to better cars and roads.
Scholars do, however, try to take these things into account and can tease out what the BAC limits do, independent of other factors.
What happened when states went down to .08? Approximately 20 scholarly analyses have found strong evidence lives were saved. The median study found that, thanks to the .08 limit, fatal crashes involving alcohol dropped by about 7 percent.
For reference, we had about 12,000 fatalities from crashes involving alcohol in 2008, so this very roughly implies an annual savings of well over 800 lives.
Other studies have reached very similar findings. D. Eisenberg found that the more strict limit cut total traffic fatalities by 2.6 percent, implying at least 1000 lives saved annually, and A.S. Tippetts, R.B. Voas, J.C. Fell and J.L. Nichols found that if all states had the .08 limit in 2000 over 900 lives would have been saved that year.
Since the drop to .08 was effective, what if we took the next step, to.05?
At least 100 studies show that driving with a BAC below our current limit of .08 — but above above .05 — is quite dangerous (see this review from H. Moskowitz and D. Fiorentino). For example, P.L. Zador, S.A. Krawchuk and R.B. Voas found that drivers with a BAC between .05 and .07 have 4 to 10 times the risk of being in a fatal crash compared to sober drivers.
Cutting the limit to .05 would be far from unprecedented. At least 52 nations have done it, including Brazil, China, India, Russia, the Nordic countries, Argentina, France, Germany, Italy, Greece, Spain, Taiwan, Thailand and Turkey. And none of their civilizations are collapsing, with the possible exception of Greece’s, and that for unrelated reasons.
Several studies have found that countries experienced positive results when they went down to .05. For example, J. Henstridge, R. Homel and P. Mackay reported that fatal crashes dropped 18 percent in Queensland, Australia and eight percent New South Wales (even controlling for other anti-DUI measures).
What would the effects be in this country? To the best of my knowledge no projections exist. But in 1998, a very thorough study by R.E. Mann, S. Macdonald, G. Stoduto, S. Bondy and A. Shaikh looked at what the effects of a national 0.05 limit would be for Canada, a country with driving and DUI levels in the same ballpark as ours.
They concluded that the adoption of a .05 BAC limit would cut motor-vehicle crash fatalities by 6 to 18 percent. To make an admittedly very back-of-the-envelope calculation, taking their most conservative estimate and applying it to the current US fatality rate indicates that perhaps 2,400 lives would be saved by this policy.
But at what cost? Well, we’d have to drink less. Determining how many drinks result in a particular BAC is extremely hazardous, since much of it has to do with factors like weight and metabolism. But to be on the safe side, drivers, particularly lighter ones, would have to limit themselves to a single drink before climbing behind the wheel.
Are hundreds or quite possibly thousands of lives a year worth this sacrifice? One could certainly make the case that the answer is “no,” given that there are millions of us who enjoy alcohol very much. Certainly there are plenty of other policy arenas where we trade off death for pleasure (smoking, motorcycle riding, junk food consumption), although most of those don’t jeopardize others the way drunk driving does. In any event, I’ll leave it up to you to decide if you’d be willing to turn that second beer into a root beer.