Motor vehicle accidents are listed as the number one cause of death for teens between the ages of 15 and 19 years old, according to the National Highway Traffic Safety Administration. Researchers have studied many factors that contribute to these unfortunate teen fatalities, and have found that speed, seat belt use, distraction, inexperience and drunk driving are just some of the factors that may be involved in teen auto accidents. One study published in the Journal of the American Medical Association, however, found a correlation between the number of passengers teen drivers have in the vehicle and their risk of being killed in an auto accident.

The study looked at fatal motor vehicle accidents involving 16 and 17-year-old teens across the U.S. Researchers measured the number of passengers that were in the car at the time of the collision, as well as the time of day the accident took place, the driver’s age and the sex of the driver. Surprisingly, the data concluded that the risk of becoming involved in a fatal car accident increased in proportion to the number of passengers teenagers had in the vehicle while driving.

As a result, many states, including Tennessee, require teens to transition through a graduated driver’s license program before they are allowed full access to the road. The program regulates when teens can drive, how many people they can drive with as well as the ages of the passengers. Researchers believe that limiting the number of passengers that teens are able to have in the car while driving can help to reduce the risk of teenage car accidents, injuries and deaths.