It’s not just what’s on the road that can cause teen drivers to crash– it’s also about who’s sitting next to them. The Children’s Hospital of Philadelphia and State Farm conducted a study to identify factors that can lead teen drivers with multiple peer passengers to get into an accident. “These studies help us understand the factors that may predispose teens to drive with multiple friends and how those passengers may contribute to crashes by distracting the driver and promoting risky driving behaviors, such as speeding, tailgating, or weaving,” said study author Allison Curry, PhD, director of epidemiology at the Center for Injury Research and Prevention in a news release. “Knowing this, we can develop programs that work in tandem with current Graduated Driver Licensing laws that limit the number of passengers for teens during their first year of driving.”

Nearly 200 teen drivers were surveyed and experts found that those who are most likely to drive with multiple passengers are those that consider themselves thrill-seekers, those whose parents don’t set rules or monitor their whereabouts, or those who don’t understand the risks of driving in general. “The good news is that that these teens make up the minority,” said Jessica Mirman, PhD, study author and a behavioral researcher in a news release. “Teens in this study generally reported strong perceptions of the risks of driving, low frequencies of driving with multiple passengers, and strong beliefs that their parents monitored their behavior and set rules.”

Another study looked at what was happening to distract the teen driver just before they crashed. Males with passengers are nearly six times more likely to break a road rule and twice as likely to drive aggressively before a crash. “Both male and female teen drivers with peer passengers were more likely to be distracted just before a crash as compared to teens who crashed while driving alone,” explained Dr. Curry. “Among the teens who said they were distracted by something inside the vehicle before they crashed, 71 percent of males and 47 percent of females said they were distracted directly by the actions of their passengers.”

The study found that parents play an important role in safe teen driving. Setting house rules of no non-sibling teen passengers for the first six months of driving can help limit accidents. “Most teens take driving seriously and act responsibly behind the wheel. However, some may not realize how passengers can directly affect their driving,” said Dr. Mirman. “Teen passengers can intentionally and unintentionally encourage unsafe driving. Because it can be difficult for new drivers to navigate the rules of the road and manage passengers, it’s best to keep the number of passengers to a minimum for the first year.”