Separating Hyperplanes

On open-container laws

Matthew Martin 11/07/2014 10:03:00 AM

Personally, I don't drink, so open-container laws don't inconvenience me at all. Nevertheless, I'm always surprised by the weirdly compelling consensus among those who do drink--even those I know who have broken this law--that having an open alcohol container in a car while driving should be illegal. I say "weirdly" because in fact, having an open alcohol container does not imply that you are under the influence--you have to actually drink the alcohol to be impaired, and that can be tested by blood test, urine test, or breathalizer. The only possible justification for an open container law is that having an open container is a reasonable proxy for being under the influence, yet this link is never actually debated.

Just so you don't think I'm barking at windmills, here's a survey showing that an expert panel of alcohol experts expressed a consensus that open-container laws were highly effective (three out of three stars) at reducing drunk driving, though they rated the evidence as weak.

There is no federal law prohibiting open alcohol containers in vehicles per se, but there are strongly coercive incentives in the transportation budget designed to force states to enact laws prohibiting open alcohol containers in vehicles. 39 states and the District of Columbia have done so, and not all at the same time, so that we have a reasonable instrument for studying the effects of this prohibition. The actual data contradict the expert opinion. Open container laws do not reduce drunk driving.

Let's start with an older paper Chaluopka, Saffer, and Grossman (1993) from the Journal of Legal Studies:

They did not publish the estimates, be cause they found no statistically significant association between open-container laws and fatalities.

Their results have held up extremely well over the years. Whetton-Goldstein et al (2000) in Accident Analysis and Prevention found essentially no effect of open container laws on traffic fatalities, alcohol-related or otherwise--the correlation was actually positive, but not statistically significant.

More recently, Chang, Wu, and Ying (2012) also in Accident Analysis and Prevention, did find a statistically significant effect of open-container laws on fatalities, especially alcohol-related fatalities:

But as in Whetton-Goldstein et al, the effect is actually positive--open container laws make the roads less safe for drivers, not more. It's not hard to tell a story about why this might be: if someone knows they cannot take a drink home to finish it there, they will attempt to finish it before driving home, thus increasing their intoxication while driving. This suggests that "drinking then driving" is a much bigger concern than "drinking and driving."

There was only one study I found that suggested open-container laws have any benefits at all. Markowitz et al (2012) in the German Economic Review looked at the correlation between self-reported victimization for violent crimes and various alcohol-related policies, one of which was the open-container law.

Results fail to find an association between the open container policy and alcohol or drug related crime. However, they found a statistically significant decrease in all violent crime associated with the policy.

They found no statistically significant correlation between the open-container policy and alcohol or drug-related crime, but did find a statistically significant reduction in all violent crime. The implication, if taken literally, is that prohibiting open alcohol containers in vehicles reduces non-alcohol-related violent crime. That's pretty hard to parse, and the authors do not seem to interpret this as a causal effect. From their introduction:

"However, our price effects are only significant at conventional levels when considering the probability of an alcohol- or drug-involved assault. Few conclusions can be drawn for the other alcohol control policies."

So despite the statistically significant result for open container laws above, "few conclusions can be drawn" about this policy from this evidence--I agree. Moreover, in their methods section:

"In interpreting the results, we caution that there may be potential endogeneity problems with all the price and alcohol policy variables, to the extent that unobserved, time-varying factors may be in the error term and correlated with both the policies and criminal violence. The fixed effects will help mitigate any time-invariant correlation, and the TCPA also minimizes this potential correlation. Nevertheless, our results should be treated as associations."

That is, they caution against a causal interpretation of their results. My guess is the one stray result was merely spurious correlation: non-alcohol violent crime rates were falling over the period they examined, so that people did report fewer victimizations after the laws passed than before, but not as a result of the law itself.

Overall, there's pretty strong evidence in the literature, both old and recent, that open-container laws do not decrease drunk driving, and may actually make it worse. No study I found actually showed any decrease in drunk driving at all as a result of the prohibition, and there is no convincing theory why this should even be expected. The law inconveniences many at no gain and possibly significant cost, so I don't understand why there is so much consensus with the status quo.

Anonymous 4/22/2015 04:02:00 PM

Earth Day, 2015. NH has an open container law but no deposit on containers. Consequently there is a strong incentive toss empties out the window when driving and drinking. Sadly, there is no shortage of blue beer cans along our roadsides. One wonders... At what 'price point' (i.e., deposit) is there a greater incentive to keep an empty in the vehicle vs tossing it out?