The risk of death from a car crash is lowest when all occupants wear seat belts, according to the Journal of the American Medical Association, because an unrestrained occupant can cause harm to others in the vehicle.

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"A car occupant could be killed if struck by another occupant," the authors of the article say.

The study estimated the association between the death of a car occupant and the use of seat belts or car seats by others in the car. The researchers restricted their study to pairs of occupants who were in the same car when they crashed, based on National Highway Traffic Safety Administration reports.

The study found that when people in the back seat were not restrained, there was a 20 greater risk of death for those in the front seat.

For a rear-seat occupant, the risk of death was increased by 22 percent if someone in front of them was unrestrained.

For a belted person on one side of the car, the risk of death was increased by 15 percent if an occupant in the same seat row on the other side of the car was not restrained.

"If the associations we have estimated are causal, use of restraints by rear seat occupants may prevent about one in six deaths of restrained front targets that would otherwise occur when a rear occupant is present. Use of restraints by front-seat occupants may similarly reduce the risk of death for all rear targets. Persons who wish to reduce their risk of death in a crash should wear a restraint and should ask others in the same car to use their restraints," the authors said.

JAMA Study: Every Passenger Should Buckle Up

Additional Information

See The Seat-Belt Study.