New study by economist Levitt determines risks of fatal crashes, strategies to reduce accidents

Drunk drivers are at least 13 times more likely to cause a fatal crash than are sober drivers, according to a new study by Steven Levitt, Professor in Economics, and Jack Porter, professor of economics at Harvard University.

Using an innovative approach to studying drinking and driving, Levitt and Porter also were able to determine which law enforcement strategies are most likely to reduce accidents caused by drunken driving. The research was supported by the National Science Foundation.

During the holiday season, which is one of the most dangerous times for people to be on the road because of increased incidents of drunken driving, police frequently launch random roadblocks to apprehend drivers. Levittís research shows that those roadblocks are less effective than increased general surveillance.

“Our results suggest that policies focused on stopping erratic drivers with greater frequency might be more successful,” write Levitt and Porter in “How Dangerous are Drinking Drivers?” in the current issue of the Journal of Political Economy. A pilot program using dedicated patrols in Stockton, Calif., reduced involvement of drunken driving crashes by 10 to 15 percent, the authors point out.

The study provides a more accurate measurement of the risks and costs of drunken driving than was available in previous studies based on data gathered at roadblocks.

To reach a more universal understanding of the impact of drinking on driving, Levitt and Porter studied fatal two-car crashes. By comparing the number of two-car crashes involving two drinking drivers, one drinking driver or no drinking drivers, they applied mathematical formulas to determine the percentage of people estimated to be driving drunk.

They looked at records from 1983 to 1993 in the Fatality Analysis Reporting System administered by the National Highway Transportation Safety Administration and calculated the percentage of fatal accidents in which police said a driver had been drinking as well as those in which the driver had been legally drunk (0.10 percent alcohol in the blood, the most common definition at the time).

They found that drivers who had been drinking were seven times more likely to cause a fatal crash than sober drivers and those who were legally drunk were 13 times more likely.

“The peak hours for drinking and driving are between 1 a.m. and 3 a.m., when as many as 25 percent of drivers are estimated to have been drinking,” Levitt said. During those hours, about 60 percent of the fatal crashes are caused by drivers who have been drinking, the research shows.

Overall, alcohol is a factor in 30 percent of fatal crashes, which cause 40,000 deaths each year and are the leading cause of death for Americans age 6 to 27.

They also used Federal Highway Administration data to help estimate the cost to society generated by the loss of innocent lives due to drinking and driving. Based on techniques often used by economists to translate the loss of human life into quantitative terms, the authors found that the average cost to society per mile driven by drunk drivers is 30 cents. The total cost to society of drinking and driving is estimated to be at least $9 billion dollars a year. Given the current probability of being arrested for drunk driving, the authors estimate that the appropriate punishment for those found guilty of driving under the influence is approximately $8,000.

Public policies to limit drinking and driving focus frequently on adding taxes to the cost of alcohol and providing criminal penalties for driving while intoxicated.

Enforcing drunk driving laws is a more effective means of reducing fatalities than increasing taxes, the research shows. Only a small fraction of those who drink alcohol drive drunk, so taxing alcohol to raise the price and reduce consumption is a very blunt tool.

States that have enacted stiff mandatory punishments for repeat drunk driving offenders or increased the number of police patrols devoted to catching drunk drivers have had greater success in lowering alcohol-related fatalities, the scholars found.