Programs that keep young drivers from taking the wheel at night, or with a car full of teens, may reduce the risk of fatal crashes in some drivers -- but increase that risk in others, according to a U.S. study.

Car crashes account for more than one-third of deaths in U.S. teens, according to the Centers for Disease Control and prevention, and are the leading cause of death for that group.

Researchers led by Scott Masten from the California Department of Motor Vehicles combined data on fatal crashes in adolescents aged 16 to 19 between 1986 and 2007, looking at graduated driver licensing (GDL) systems.

In the United States, stronger GDL programs with restrictions on nighttime driving as well as allowed passengers, relative to programs with some of the key GDL elements, were associated with substantially lower fatal crash incidence for 16-year-old drivers but somewhat higher fatal crash incidence for 18-year-old drivers, Masten wrote in the Journal of the American Medical Association.

Future studies should seek to determine what accounts for the increase among 18-year-old drivers and whether refinements in GDL programs can reduce this.

Starting in 1996, U.S. states began putting restrictions on drivers under 18, including on what hours they could take the wheel -- not after midnight, for example -- and who they could have as a passenger, including no more than one other teenager. Now, every state has some degree of these programs.

Masten and his team found that on the whole, fewer teens died in car crashes when stricter diving policies were in place.

With no driving restrictions, about 47 of every 100,000 teens died in a car crash each year, on average. With strict programs, including both nighttime driving and passenger restrictions, that decreased to 30 in every 100,000 per year.

When the researchers accounted for other factors, including how often people drove in each state and in what season car crashes occurred, they found that 16-year-olds were 26 percent less likely to die in a crash when states had strict driving restrictions than when they had none.

However, 18-year-olds -- who no longer faced the restrictions -- were 12 percent more likely to have a fatal crash. There was no difference in fatal crash rates for 17- or 19-year-olds.

Statistical tests couldn't confirm any difference in crashes among all 16-to-19-year-olds combined, with or without the driving policies.

Based on those findings, they calculated that since 1996, graduated driving licensing programs have been linked to 1,348 fewer fatal crashes in 16-year-old drivers and 1,086 more of those deaths in 18-year-olds.

Teens learn well and react well, said Jean Shope, from the University of Michigan Transport Research Institute, who was not involved in the study.

If we want teens to get driving experience while they're teens, we have to face the fact that they are teenagers and still have development issues going on.

She added that some experts have wondered whether more young drivers will wait to get their licenses at age 18 to avoid restrictions that only apply to younger teens.

Another possibility is that even teens who get a license earlier will have less experience driving along and under challenging conditions when they hit 18, other experts said.

Anne McCartt, from the Insurance Institute for Highway Safety in Arlington, Virginia, said that national trends have generally shown a drop in teen crashes since restrictions went into effect.

I think these studies may help us identify ways to make teens even safer, but we've been doing a much better job than we used to, she added. SOURCE: