A study released Tuesday by the American Automobile Association says it's dangerous for teens to drive with friends in their car.

The risk of 16- and 17-year-old drivers being killed in a car crash increases with each additional passenger under 21, according to a new report titled "Teen Driver Risk in Relation to Age and Number of Passengers."

"Per mile driven, drivers under the age of 20 have higher rates of involvement in fatal crashes than drivers of any other age group except drivers aged 80 and older," the study says.

The AAA Foundation for Traffic Safety study was undertaken to update data that was more than a decade old showing that the presence of passengers in a vehicle increased the risk of fatal crash involvement for teenage drivers. For the new study, researchers examined data on car crashes that occurred in years 2007 to 2010 as well as data on the number of miles driven in years 2008 to 2009.

According to the study, the fatality risk to 16- or 17-year-old drivers:

  • Increases 44% when carrying one passenger younger than 21 (and no older passengers)
  • Doubles when carrying two passengers younger than 21 (and no older passengers)
  • Quadruples when carrying three or more passengers younger than 21 (and no older passengers).
  • Carrying at least one passenger age 35 or older cuts a teen driver's risk of death by 62 percent and the risk of involvement in any police-reported crash by 46 percent

"These results show that although the overall number of teen driver fatalities has decreased substantially over the past several years, carrying young passengers is still a significant risk factor for young drivers," the study says. "In contrast, carrying adult passengers significantly reduces the risks of crash involvement."

To read the study in full, go to: http://www.aaafoundation.org/pdf/2012TeenDriverRiskAgePassengers.pdf.