Substance abuse treatment and motor vehicle fatalities.

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Substance abuse treatment and motor vehicle fatalities.

1. Introduction

In recent years, motor vehicle accidents have led to over 40,000 deaths annually in the United States, and alcohol-related accidents account for about 40% of these deaths. Legally drunk drivers are much more dangerous on the road than sober drivers, (1) so considerable effort has been devoted to reducing the incidence of alcohol-impaired driving. Policies targeting drunk driving include alcohol taxes, increases in the legal drinking age, educational efforts, more stringent blood alcohol content (BAC) limits, and increased punishments for those arrested for driving under the influence of alcohol (DU1). (2) In this article we evaluate the impact of an additional policy instrument for reducing the incidence of drunk driving: the supply of substance abuse treatment (SAT).

In 2006, an estimated 22.6 million U.S. residents were classified with substance dependence or substance abuse problems. Only 30% of this group, however, received treatment for alcohol abuse or drug addiction. (3) There is abundant evidence that SAT reduces drug and alcohol abuse, specifically among heavy users. (4) A reduction in dangerous driving behavior is just one of the positive effects of successful SAT; others include improvements in physical health, employment performance, and happiness at home. Substance abuse treatment also has the advantage of being a lower-cost approach to consumption reduction compared to criminal justice interventions in alcohol and drug abuse. (5)

In order to assess the impact of increased SAT on reductions in traffic fatalities, we would ideally observe data on the individuals who desire or require treatment, which individuals do and do not receive treatment, the subsequent drug and alcohol consumption of the treated and untreated, and finally the differences in driving behavior of the treated and untreated populations. Data at this level of detail on substance abuse, treatment, and driving are simply unavailable, so in this article we employ coarser measures of SAT in the United States. (6) We observe the numbers of SAT clinics and traffic fatalities in non-metropolitan U.S. counties, where the extent of treatment can be measured by the number of local SAT clinics. We effectively assume that an increase in the number of SAT clinics reduces the costs or inconvenience for the local population to receive treatment. As more individuals receive treatment, the safety of driving behavior increases on local roads. Our approach, therefore, is conservative in the sense that we do not capture the opportunity of one county's residents to take treatment in a neighboring county, or the beneficial impact of successful SAT on driving in areas other than a person's home county.

We face a considerable challenge in establishing a causal link between SAT and traffic fatalities. Even if increasing SAT truly reduces dangerous driving, many factors that are difficult or impossible to observe can interfere with correctly making this inference. For...

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