The mandatory, phased introduction of passive restraint systems for the federal market has placed an increasing emphasis on the careful selection of suitable designs using a systematic approach.

Austin Rover Group's experiencein the use of computer aided design analysis facilitates the use of such an approach and the implementation of the chosen design. This paper follows the progress of such a design process on a specific vehicle.

At the outset of the project, only belt based restraints were considered, but there were three possible approaches. Each was modelled and compared in different crash environments using c omputerized crash victim simulation (CVS). Attention was given to recognized injury criteria and the constraints imposed by other features of the vehicle concept.

From the model of the chosen system, worst-case loadings and energy absorptions were used by design areas to verify and develop specific items. In particular the fascia integrated knee bolsters and seat structure. In both cases finite element analysis methods were used.

For the bolsters the criteria involved maximum force levels and absorption of energy and for these a non-linear analysis with large displacements was applied. In the time available, an exhaustive study was not possible, but the computer analysis was used to highlight areas of strength and weakness by predicting the collapse mode. The bolsters were tested both individually and as part of the complete fascia to confirm the design performance. They were also tested as part of the full restraint system in a Hyge Sled Test using two dummies and realistic decelerations.

A full crash test confirmed the effectiveness of the system.