The team examined the records of drivers in Ontario, Canada, and found that receiving a traffic ticket reduces a driver's risk of dying in a crash by 35 percent in the weeks following the citation. "You don't think the police are doing a public service when they issue tickets, but traffic enforcement has a huge public-health benefit," said Tibshirani, professor of health research and policy at Stanford and study co-author. "It may be a nuisance to receive a ticket but it could be helpful."
One million people die and 25 million people are permanently disabled from traffic crashes worldwide each year, the researchers report in their study. While limited evidence previously has pointed to traffic enforcement reducing fatalities, the researchers' aim in this study was to learn whether receiving a ticket has a protective effect on the driver.
"Getting a ticket stays on your mind," said Tibshirani when explaining why traffic enforcement could influence the way people drive. "If you know you deserved the ticket it may remind you to slow down."
The researchers studied public records of 8,975 drivers who had been involved in fatal crashes in Ontario between 1988 and 1998. They found the drivers had 21,501 total tickets for moving violations prior to the date of the crash, averaging about one ticket per driver every five years.
The researchers found that 135 drivers had a traffic ticket in the month before the crash and 204 had a conviction in the same month one year before. Their analysis indicated that the risk of a fatal crash in the month following a conviction was nearly 35 percent lower than in a month with no conviction. The benefit existed for drivers regardless of age, prior convictions and other personal details. The highest life-saving benefits were for drivers who had received convictions that carried a $100 fine and three penalty points against their driver's license (the penalty for exceeding the speed limit by 20 kilometers per hour or about 12 mph). This protective effect lasted for one to two months and was insignificant after four months.
Tibshirani was surprised by the findings. "I didn't expect to find anything," he said. "Although a speeding ticket makes me drive more carefully, I thought the protective quality would be too small to detect."
The researchers said their data also suggest that one life is saved for every 80,000 tickets issued; one emergency department visit is prevented for every 1,300 tickets; and $1,000 in societal cost is saved for every 13 tickets. Because traffic laws in Canada and the United States are similar, Tibshirani said the findings should apply in both countries.
Based on the data, Tibshirani and his co-authors said increasing traffic enforcement measures might further reduce total deaths; conversely, inconsistent traffic enforcement could contribute to thousands of deaths each year. They said their findings could help determine the allocation of scarce police resources toward traffic safety efforts and could also inform debates on the use of new enforcement technologies such as cameras that snap pictures of red-light runners.
The researchers acknowledged that the exploration of additional traffic enforcement may not be welcomed by the public, however. "The major impediment to general traffic enforcement is a lack of public support," the researchers note in the paper. "Unlike vaccination or other preventive care, individuals are not gracious at the prospect of a conviction and often resist with subterfuge or argument."
Tibshirani said public-health measures are often unpopular, but he hopes this issue will be viewed differently. "It would be nice if this study had an impact on public perception and people recognized that traffic enforcement can save a lot of lives."
The study was led by Donald Redelmeier, MD, professor of medicine at the University of Toronto. Leonard Evans, with Science Serving Society, a Michigan-based think-tank, also collaborated on the study. The study was funded by a grant from the Canadian Institutes for Health Research, a Career Scientist grant from the Ontario Ministry of Health and the de Souza Chair in Trauma Research at the University of Toronto.
Stanford University Medical Center integrates research, medical education and patient care at its three institutions - Stanford University School of Medicine, Stanford Hospital & Clinics and Lucile Packard Children's Hospital at Stanford. For more information, please visit the Web site of the medical center's Office of Communication & Public Affairs at http://mednews.stanford.edu.
Journal
The Lancet