The most common type of injury after a car crash is the acceleration-deceleration injury. After a rear impact collision, which is the most common type of car crash, the vertebrae in your neck overextend. The result is whiplash. Seatbelts make other more serious types of injuries far less likely, but the fact that they restrain you means that you are vulnerable to whiplash.
Other car accident injuries are caused by blunt impact when motor vehicles collide. In cases where seatbelts are not worn, there are two collisions: the first is between the two vehicles. The second occurs when you continue to accelerate before impacting against surfaces inside your car. The result can be spinal cord injuries, bruises, broken bones, and other trauma.