Health insurance mandates and traffic fatalities: The effects of substance use disorder parity laws

Impaired driving is a major public safety concern within the United States. Impaired drivers increase the risk of traffic accidents for themselves, their passengers, and other drivers. For example, each year over 10,000 individuals are killed in alcohol-involved traffic accidents, representing nearly one third of all traffic-related deaths. Moreover, psychoactive drugs are involved in nearly 20% of all fatal traffic accidents. These statistics suggest that the social costs of impaired driving are very high. In response, governments of all levels have taken steps to reduce impaired driving by setting maximum allowable levels of alcohol drivers may legally consume, prohibiting driving while under the influence of psychoactive drugs, instituting roadside check points, financing media campaigns, and so forth. A potential policy approach to address impaired driving is to reduce the prevalence of substance use disorders (SUD) within the population through effective and affordable treatment. SUDs are chronic health conditions that can be treated medically, rather than punitively, for many afflicted individuals. Reducing SUDs should reduce the number of impaired drivers on roadways, and hence traffic accidents attributable to impaired driving. Although treatment has been shown to effectively reduce SUDs, many individuals who could benefit from such treatment do not receive it. A commonly cited barrier to treatment receipt is cost. Indeed, within the U.S., insurance plans (public and private) have historically covered SUD treatment less generously than medical/surgical treatment. For example, cost-sharing (e.g., copayments) has historically been higher for SUD treatment than for medical/surgical treatment. In this study we explore the extent to which state parity mandates for SUD treatment affect fatal traffic accidents. State parity mandates regulate private insurance markets. These laws expand coverage for SUD treatment by requiring private insurers to cover SUD treatment services at parity with medical/surgical services in terms of cost sharing and service limitations. Previous research documents that these mandates increase SUD treatment utilization. To explore the effect of state parity laws on traffic fatalities, we use administrative data from the Fatal Accident Reporting System between 1988 and 2013. During this period, 12 states passed SUD parity mandates, offering a quasi-experiment with which to study the effects of these laws on traffic fatalities. We apply differences-in-differences methods to study this question. In an extension, we use vital statistics data from the Centers for Disease Control and Prevention to examine the extent to which state parity mandates affect fatal alcohol poisonings and psychoactive drug overdoses. Reduced substance misuse is the key channel through which we expect mandates to affect traffic accidents. Our findings indicate that passage of a parity law reduces traffic fatality rates by 7.6% to 8.2%. We also find that passage of parity laws reduces fatal alcohol poisonings and psychoactive drug overdoses. These findings suggest that government regulations, such as those codified within the Affordable Care Act, that require insurers to cover SUD at parity with medical/surgical services can improve traffic safety by reducing the number of impaired drivers on roadways, in addition to reducing the level of substance misuse within the population.