NSF PR 01-106 - December 19, 2001
Drunken Driving Costs and Risk Measured More Accurately
Drunk drivers are at least 13 times more likely to
cause a fatal crash than sober drivers, according
to a new study by Steven Levitt, Professor of Economics
at the University of Chicago and Jack Porter, Professor
of Economics at Harvard University.
Using an innovative approach to studying drinking and
driving, Levitt and Porter were also 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 (NSF).
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.
Levitt's 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, Cal., reduced
involvement of drunk driving crashes by 10-15 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 are able
to apply 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
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 time periods, 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 aged six
They also used Federal Highway Administration data
to help estimate the cost to society generated by
loss of innocent lives due to drinking and driving.
For each arrest, the cost to society would be $8,000
based on standard economic estimates for the value
of a person's life. That cost shared among all drinking
drivers, including those not involved in fatal crashes,
would be 16 cents a mile for drinking drivers and
30 cents per mile for those who are legally drunk.
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. The results of enforcement
are uneven among drinkers, however, the scholars said.
"Interestingly, higher beer taxes and tougher punishments
for first-time offenders are generally associated
with greater danger posed by drinking drivers on average"
because the people who choose not to drive are less
drunk than the remaining pool of drivers who have
been drinking, the scholars found.
The most effective way to decrease overall fatalities
is punish "a relatively small fraction of hard-core
drunk drivers," the paper points out. Although the
punishments do not reduce the numbers of drunken drivers,
those who are drunk drive with more care.