Study examines how, why states adopt drunk driving laws

A new study by public health researchers at NYU's Steinhardt School of Culture, Education, and Human Development finds that the severity of the problem within the state is not the most important predictor of whether states adopt new laws to restrict drunk driving -- nor is the political makeup of the state government. Instead, the two strongest predictors of states adopting their first drunk driving laws were having a large population of young people and a neighboring state with similar driving laws.

The findings, published in the American Journal of Public Health, suggest that state lawmakers look at factors both within their states as well their neighboring states when considering new driving laws.

"Although we did not find the overall traffic-related fatality rate to predict policy adoption, the size of the population ages 15 to 24 years -- the group most at risk for death and injury from impaired driving -- was associated with first time policy adoption, suggesting that states might be initially more receptive to regulation when it involves protecting younger populations," said study author Diana Silver, associate professor of public health at NYU Steinhardt and NYU College of Global Public Health. "At the same time, going forward, the makeup of the state's population did not predict whether states would adopt subsequent laws."

Recent estimates suggest that as many as 20,000 people in the U.S. are killed each year in car accidents because of a failure to adopt the full range of approaches to enhance motor vehicle safety. While there is evidence that improving driving laws -- which are regulated state by state -- can improve health, little is know about why states have approached the regulation of driving laws in such different ways.

In the study, the researchers looked at seven state-wide laws on alcohol-impaired driving adopted between 1980 and 2010: a 0.08 limit on blood alcohol content; a ban on open alcohol containers; zero tolerance laws for drivers under the age of 21; and license suspension, minimum fines, mandatory community service, and minimum prison time for driving under the influence. The researchers analyzed each state's adoption of the laws from 1980 to 2010 to identify predictors of first-time and subsequent law adoption.

They then compared the adoption of these laws to both internal and external state factors. Internal factors included the political environment, state resources, legislative history, population characteristics, unemployment rate, alcohol consumption per person, taxes, and traffic fatality rates. External factors measured were the neighboring states' history of law adoption and changes in federal law.

The authors found that neighboring states' adoption of laws was quite influential, as was the state's own history of prior law adoption. Contrary to expectations, the political makeup of the state's government was not predictive of greater regulation.

"Republican or Democratic governors, divided state legislatures -- none of those factors predicted more regulation of drunk driving," said Silver.

The researchers saw an increase in the number of all seven alcohol-impaired driving laws from 1980 to 2010, but the pattern of adoption for each state varied by law. The only two laws adopted by all states (zero tolerance laws and limiting blood alcohol content to less than 0.08) were actually prompted by federal action and incentives.

"Right now, states offer very different levels of protection from drunk drivers on the road," noted Silver.

"Organizations seeking to stimulate state policy changes may need to craft strategies that engage external actors, such as neighboring states, in addition to mobilizing within-state constituencies," said James Macinko, professor of public health at UCLA and the study's coauthor.