"By supporting the entire posterior torso, neck, head, and pelvis, a rear-facing car seat (RFCS) distributes crash forces over the entire body rather than focusing them only at belt contact points. In contrast with a forward-facing car seat (FFCS), an RFCS supports the child’s head, preventing the relatively large head from loading the proportionately smaller neck with relatively weak neck musculature.

...In the USA, the American Academy of Pediatrics and the National Highway Traffic Safety Administration (NHTSA) have developed guidelines stating that a child should be at least 1 year of age and weigh at least 20 pounds before transitioning from an RFCS to an FFCS.4 5 The age of the child, in particular, is an important factor which correlates with the material properties of the child’s anatomy, such as muscular development and ossification of the cervical spine. Although the policy of the American Academy of Pediatrics states ‘‘for optimal protection, the child should remain rear facing until reaching the maximum weight for the car safety seat, as long as the top of the head is below the top of the seat back’’, a common interpretation of these guidelines by parents and caregivers has been that children should be automatically switched to an FFCS when they are 1 year old or 9.2 kg (20 pounds). For this reason, few children in the USA remain rear facing past their first year of age, despite the fact that there are currently many RFCSs that have maximum weight limits beyond 9.2 kg.