A planar mathematical model was developed to provide means of studying factors which can influence the function of lower torso restraint via a padded lower instrument panel or knee bolster. The following factors were judged to play the most significant role:
initial fore-and-aft position of the seated occupant relative to the knee restraint;
location of the knee-to-bolster contact;
angular orientation of the bolster face;
primary axis of the bolster resisting force, 5) variations in vehicle crash parameters (e.g., toepan rotation and displacement and seat deflection); and 6) deformation characteristics of the bolster. The model of a seated occupant included radiographic and empirical data on the anatomy of the links and joints in the lower extremity. Emphasis was also placed on determining a range of reference location, orientation and primary axis of resistance of the knee bolster so that an effective restraint may be provided for the 5th percentile female, 50th percentile male, and 95th percentile male occupant.