Protecting Child Passengers in the Vehicle
There are three “collisions” that occur in every crash where occupants are unrestrained. The first collision involves the vehicle and another object, e.g. another vehicle(s), a stationary object (tree, signpost or ditch) or a human or animal. The second collision occurs between the unbelted occupant and the vehicle interior, e.g. the driver hits his chest on the steering wheel or his head on the window. Finally, the third collision occurs when the internal organs of the body hit against the chest wall or the skeletal structure.
It is the second collision that is most responsible for injuries, and can be reduced significantly by the use of seat-belts and child restraints. The most frequent and most serious injuries occurring in frontal impacts to occupants unrestrained by seat-belts are to the head, followed in importance by the chest and then the abdomen. Among disabling injuries, those to the leg and neck occur most frequently.
When a crash occurs, a car occupant without a seat-belt will continue to move at the same speed at which the vehicle was travelling before the collision and will be catapulted forward into the structure of the vehicle – most likely into the steering wheel if they are driving, or into the back of the front seats if they are rear seat passengers. Alternatively, they can be ejected from the vehicle completely.
At birth, the infant head is around a quarter of their total length and about a third of their body weight. An infant’s skull is very flexible, so a relatively small impact can result in significant deformation of the skull and brain. The smaller the child, the lower the force needed for injury. The infant rib cage is also very flexible. Impact to the chest can result in a large compression of the chest wall onto the heart and lungs, and some of the abdominal organs. The infant pelvis is unstable and cannot withstand the forces from an adult restraint system. Infants require their own special seat designed to cradle them in a crash, and provide protection from many types of crashes.
Like adult seat-belts, child restraints in cars are intended to keep a child firmly secured in their seat so that in the event of sudden braking or collision the child is not thrown against the car interior or ejected from the vehicle. The restraint must absorb kinetic energy (created by the motion of the child during the crash) without itself injuring the child and must be easy to use.
