Most drivers and passengers killed in crashes are unrestrained. 53% of drivers and passengers killed in car crashes in 2009 were not wearing restraints.1

Seat belts dramatically reduce risk of death and serious injury. Among drivers and front-seat passengers, seat belts reduce the risk of death by 45%, and cut the risk of serious injury by 50%.4

Seat belts prevent drivers and passengers from being ejected during a crash. People not wearing a seat belt are 30 times more likely to be ejected from a vehicle during a crash. More than 3 out of 4 people who are ejected during a fatal crash die from their injuries.5

http://www.cdc.gov/motorvehiclesafety/seatbeltbrief/