Car seats are designed to absorb some crash forces and spread the remaining crash forces over a larger area of the body. For adults, seat belts distribute force to the strongest parts of the body—the hips, chest bone, and collarbone. When forward-facing, the head pulls forward, which puts stress on the neck. When rear-facing, the head, neck, and back all move in unison and are cradled by the shell of the rear-facing car seat.4 This video helps explain.
The bones running down a young child's neck and back are not yet solid bone (they still have a lot of stretchy cartilage). A young child's head is also much heavier, in proportion to the body, than that of an older child or adult. So the head pulls forward with proportionately much more force on bones that are stretchier. As the bones stretch, they can force the spinal cord to stretch. After it is stretched more than one-quarter of an inch, the spinal cord breaks. Riding in a rear-facing car seat helps reduce that risk by supporting the child's head.4
The incidence of severe head and neck injuries for babies and toddlers is greatly reduced in rear-facing car seats.
The additional support the rear-facing car seat provides to the head and neck reduces your child's chance of being injured or worse in a crash. The rear-facing car seat is absorbing some of the energy of the crash, and then distributing the remaining energy along the child’s head, neck and back. With the forward-facing child, the car seat isn't able to absorb as much of the energy, and more of it is transferred to the child—in particular to the head and neck as they pull away from the chest.5 The difference can be seen in a video comparing rear-facing and forward-facing car seats in a crash test.
Children are especially vulnerable in the event of a car crash. Their heads are disproportionately heavy in relation to the rest of the body and the neck muscles are not yet fully developed. Frontal impact tests show that the strain on the neck is five times greater when the child is sitting forward facing compared to when sitting rear facing.
When sitting forward facing, the child’s body is pushed out of the seat. But as the child car seat’s internal harness holds the child’s upper body in place, the majority of the forces are placed on the child’s neck as the head is thrown forward with tremendous force. In addition, the child risks injury from hitting the front seats.
If the child is sitting in a rear facing child car seat, the seat shell will act as a protective shield and absorb the impact energy. The forces of the impact are spread over the whole large area of the child’s back, neck and head, thereby significantly less strain is put on the child’s neck.