09/15/2011 10:05 am ET Updated Nov 14, 2011

License Restrictions Lower Chances Of Fatal Car Crashes Among Young Teens, Not Older Teens, Study Says

Strict license restrictions might curb the chances of younger teens being involved in fatal car crashes, a recent study found.

States enforcing graduated driver licensing systems that place restrictions on supervised and nighttime driving for young teens "were associated with substantially lower fatal crash incidence for 16-year-old drivers," according to a study published in the Journal of the American Medical Association.

However, the results also suggest that those states have higher fatal crash rates for 18-year-old drivers.

Researchers analyzed car accidents nationwide from 1986 through 2007 involving teens ages 16-19.

A possible explanation for the incidence-rate discrepancy among age groups could be attributed to teens who wait until they're older to obtain driver's licenses.

Some states only enforce the restrictions on new drivers under the age of 18, The Associated Press reports. Meaning, if a new driver is 18 years old, he or she would not technically need to follow supervision guidelines, which might encourage teens to push back obtaining a license.

At age 18, teenagers are considered adults and may be able to get a driver's license in weeks, NPR points out.

"They're saying, 'Forget it. I'll wait till I'm 18,'" lead researcher Scott V. Masten told "We have, at least in California, more novice 18- and 19-year-olds with no driving experience."

Reuters reports:

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.

Some teens say they're postponing their licenses because they can't afford a car or their parents are too busy to provide supervision, according to NPR.

The study does not provide an explanation for why more 18-year-olds were involved in fatal crashes. Scientists state more research is needed to help explain the correlation and explore ways to "reduce this association."