Car crashes are the leading cause of death for American teenagers, with about 2,500 teens dying in accidents per year, according to the National Highway Traffic Safety Administration.

Safe Kids Worldwide has conducted a national study called "Teens in Cars" to find out what causes crashes as well as what measures would help lessen the number of accidents and their effects, Edmunds.com reported.

Unsurprisingly, teens have a difficult time saying something if a driver is being unsafe; 40 percent of teens surveyed said they would speak up, but 39 percent said they would overlook it.

While surveying 1,051 U.S. teens, Safe Kids Worldwide discovered that 23 percent of them don't always buckle their seatbelt. Another unsafe behavior is phone use while driving. According to the study, 39 percent of teens surveyed had ridden with a teen driver who was texting, while 95 percent believed other teen drivers have also texted while at the wheel.

Of the teens surveyed, 43 percent said they had been a passenger in a car where the teen driver was talking on the phone.

"It can be uncomfortable for anyone to speak up when they feel unsafe riding in a vehicle, and perhaps even more so for teens riding with their peers," said Mike Robinson, GM vice president of Sustainability and Global Regulatory Affairs, in a statement quoted by Edmunds. "The results of this research further underscore the importance of reaching teens with the life-saving messages to buckle up during every ride and to speak up when they don't feel secure."

In the most recent year for which statistics were collected, 12 percent of teen drivers involved in fatal crashes were distracted by a phone or another diversion at the time, according to the NHTSA.

Safe Kids Worldwide recommended such safety measures as teaching children from a young age to wear a seatbelt; setting an example for teens by meticulously following road rules; and encouraging teens to share concerns if the driver they're riding with is being unsafe.

The survey was funded by a grant from the General Motors Foundation. 

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