How to wear a seat belt

One of the most effective measures to prevent injury and death in a crash is to be appropriately restrained. The National Highway Safety Administration estimates that lap/shoulder seat belts, when used correctly, reduce the risk of fatal injury to front seat passengers by 45 percent and the risk of moderate-to-critical injury by 50 percent.

Teens are less likely to buckle up than other age groups. When coupled with an increased likelihood for teens to be involved in a crash, this can lead to tragic consequences.
Belted occupants are less likely to be ejected from a vehicle in the event of a crash. Risk of serious injury or death rises dramatically for occupants ejected from a vehicle.
Tips for a properly fitted seat belt:

• The shoulder belt should cross the middle of your chest and away from your neck.
• The lap belt should fit across your hips, just below your stomach.
• Never place the shoulder belt behind your back or under your arm.

http://teendriving.statefarm.com/road-to-safety/auto-safety/seat-belts