Frontal impact simulations with 25 different types of child restraint systems have been made with Alderson 3 and 6 years old anthropometric dummies. Impact speed has been 50 km/h and deceleration levels 15-20 g. Electrical measurements, according to SAE J 211a, have included dummy head and chest accelerations, sled acceleration and forces acting on the restraint systems. High-speed photography has also been used.
The most significant difference between various types of systems has been that the resultant head acceleration and the hyperflexion of the neck is considerably lower with rearward facing seats compared with forward facing seats, cushions, shells and harnesses. It is proposed that, when using the test methods decribed in this paper, the following main performance criteria shall be met:
This implies that, among the systems existing today, only rearward facing seats can be approved, Behaviourial studies and experience from the 100,000 rearward facing seats used in Sweden confirm that this is a practical and usable design concept for a child restraint system.