Experts also note that the front portion of the brain, which includes the capacity to control impulses, judgment and decision-making, and coordinate multitasking, matures late--deep into the 20s.
The impact of alcohol
Research shows teens are more likely to speed and less likely to wear seat belts or recognize hazardous situations.
Add alcohol to the mix and a teenager behind the wheel of a car can be a very volatile, random and deadly combination.
But, liquor is only one of the factors.
Statistics from the Insurance Institute for Highway Safety show that alcohol is a factor in only 15 percent of the 16- and 17-year-old drivers killed in 2004 car wrecks in the U.S.
An extensive report in 2005 by the Allstate Foundation, a non-profit subsidiary of the insurance giant, showed that drunken driving "accounts for less than 25 percent of all teen crash fatalities."
In fact, alcohol may be less a factor in teen-driving deaths than it is for adults. In Illinois, 28 percent of drivers ages 20 and younger who were involved in fatal crashes in 2004 were known to have alcohol levels over the legal limit, compared with 35 percent for the overall driving public, said Joyce Schroeder, a data analyst with the Illinois Department of Transportation.
Through February, IDOT officials have recorded at least 11 crashes in the six-county Chicago region in which teens were killed and a teen driver was involved. Those crashes resulted in 16 teen deaths.
And authorities say alcohol was a factor in at least three of those fatal crashes involving teen drivers.
Understanding the full role that alcohol and drugs play is complicated.
"There are circumstances that preclude testing. If they are injured, they may be taken to the hospital and their bodies may be filled with chemicals that affect the testing," Schroeder said. "It's not a simple, straight-forward question."
More riders, more risk
A more critical factor than alcohol and drugs may be the number of young passengers in the car, research shows.
A Johns Hopkins University study that broke down the driver death rate per 10 million trips showed the rate for a 16-year-old driver rose sharply with every passenger age 13 to 29.
When the driver was alone, that death rate was 1.99 per 10 million trips. When that driver was accompanied by one passenger, the driver death rate grew to 2.76 deaths per 10 million trips.
With two passengers, the rate was almost 3.7. And when three or more passengers were in a car driven by a 16-year-old, the driver death rate per 10 million trips rose to 5.61, the study showed.
Another factor is driver error, something of a catchall category investigators use because, in many cases, it is hard to find out precisely what occurred just before a crash, said Rob Foss, senior research scientist and manager of alcohol studies at the University of North Carolina Highway Safety Research Center.
Speeding is another frequent component in teen-driving crashes, Foss said.
"There are so many factors that are so situation-specific that come into play that we can only explain a tiny fraction of why crashes occur," Foss said, adding that most of the rest are tossed into the "driver error" category by default.
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