For more than a decade, California and other states have kept their newest teen drivers on a tight leash, restricting the hours when they can get behind the wheel and whom they can bring along as passengers. Public officials were confident that their get-tough policies were saving lives.
Now, though, a nationwide analysis of crash data suggests that the restrictions may have backfired: While the number of fatal crashes among 16- and 17-year-old drivers has fallen, deadly accidents among 18-to-19-year-olds have risen by an almost equal amount. In effect, experts say, the programs that dole out driving privileges in stages, however well-intentioned, have merely shifted the ranks of inexperienced drivers from younger to older teens.
"The unintended consequences of these laws have not been well-examined," said Mike Males, a senior researcher at the Center on Juvenile and Criminal Justice in San Francisco, who was not involved in the study, published in Wednesday's edition of the Journal of the American Medical Assn. "It's a pretty compelling study."
The combination of immaturity and inexperience makes teen drivers particularly vulnerable to motor vehicle accidents. Car crashes are the leading cause of death among teens, resulting in 4,054 fatalities in 2008, according to the Insurance Institute for Highway Safety in Arlington, Va.
Graduated driver licensing programs, as they are known, bar young drivers from certain higher-risk situations — such as being on the road at night, talking on cellphones and driving with passengers — until they gain more experience. The first program was implemented in Florida in 1996, and since then all 50 states and the District of Columbia have adopted some type of multi-step plan.
Though the program details vary significantly by state, they typically set a minimum age for earning a driver's permit and a driver's license and require a certain number of hours behind the wheel while supervised by an adult. Additional driving restrictions may come into play for the first six months or year of unsupervised driving.
California, which implemented its program in 1998 and strengthened it in 2006, has one of the nation's strictest programs. After passing a driving test, teens are issued a 12-month provisional license that prohibits them from driving between 11 p.m. and 5 a.m. and from carrying passengers under the age of 20 unless an adult age 25 or older is present. If the provisional period is completed without any suspensions or probation orders, teens get a full license.
To assess the value of such programs, a team led by Scott V. Masten of the Department of Motor Vehicles Research and Development Branch in Sacramento examined data on more than 131,000 fatal crashes involving teen drivers from all 50 states and the District of Columbia between 1986 and 2007. The long period allowed the team to compare data from states with graduated licensing programs with data from those that had not yet adopted a program.
The researchers found that states with the most restrictive graduated licensing programs — such as those that required supervised driving time as well as having night-driving restrictions and passenger limitations — saw a 26% reduction in the rate of fatal crashes involving 16-year-old drivers compared with states without any restrictions.
But the rate of fatal crashes among 18-year-old drivers in those states jumped 12% compared with the states without restrictions. The analysis controlled for other factors that could affect road safety, such as laws regarding seat belts and allowable blood-alcohol levels.
A similar trend was seen when comparing drivers in states with strong graduated licensing programs with those in states with weak programs: The rate of fatal crashes among 16-year-old drivers was 16% lower but was 10% higher among 18-year-old drivers.
Overall, since the first program was enacted in 1996, graduated programs were linked to 1,348 fewer fatal crashes involving 16-year-old drivers and 1,086 more fatal crashes involving 18-year-old drivers.
"The programs reduce crashes among 16-year-olds — if you look at just that, it looks bright and shiny," Masten said. "But there appears to be some negative consequences. Instead of just looking at the targeted group, we need to ask what is going on with all teens."
Experts said it's not clear why fatal crash rates are higher among 18-year-olds in states with stronger graduated driver licensing programs. One possibility is that teens in these states may be waiting until they turn 18 to apply for a license because that allows them to bypass the restrictions.
According to the California DMV, the rate of 16-year-olds licensed to drive unsupervised fell from 23% in 1997 to 14% by 2007. As a result, "we have more novices on the roads at ages 18 and 19," Masten said.
Not everyone is convinced that the programs are backfiring, however.
A study published last year in the journal Traffic Injury Prevention found that the rate of fatal crashes for 15-to-17-year-olds was 30% lower in states with strong graduated licensing programs compared with states with weaker programs — but the accident rate for 18- and 19-year-olds was essentially the same under both regimes.
"Our studies did not find a negative effect" on older teens, said coauthor Anne T. McCartt, senior vice president of research at the Insurance Institute for Highway Safety. "We think the bigger the benefits for the younger teens, the more likely there is an overall positive effect for teens as a whole."
To get at the truth, researchers may need to dig into the data on individual state programs instead of grouping all states together, said Susan P. Baker, a professor at the Johns Hopkins Bloomberg School of Public Health who has studied the graduated programs but was not involved in either study. That would allow for a cleaner assessment of a program's value, she said.
McCartt said the solution may be to expand graduated driver licensing programs to include 18- and 19-year-olds who are getting behind the wheel for the first time. The idea isn't without precedent: In New Jersey, such rules apply to all initial driver's license applicants under the age of 21.
"The concept of easing drivers into riskier driving situations could apply to older teens as well," she said.
But Males, who has studied California's program, said it was inappropriate to impose such restrictions on legal adults and noted that the rules could disqualify them from holding certain jobs.
"That's a terrible idea," he said. "That's saying the programs didn't work, so we'll have to make them even stronger."