A teenage driver’s risk of dying in an accident increases dramatically when there are other teens in the car, and plummets when there’s an adult looking on, according to a study by AAA’s safety foundation.

Researchers have long known that the presence of other teens is distracting to novice drivers, but most previous studies on the issue are more than a decade old and don’t reflect changes in state driving laws that began in the mid-1990s. Since then, every state has adopted a “graduated licensing” law that places some restrictions on teen drivers. The laws vary, but typically they restrict teens from driving with any passengers under age 21, or just one young passenger, and bar nighttime driving.

The study by the Automobile Association of America’s Foundation for Traffic Safety, being released Tuesday, found what a lot of parents already know: Teens driving with their friends in the car continues to be far riskier than driving alone or with an adult. The study was based on an examination of government data on teen crashes from 2007 to 2010.

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