The need is pointed out for more comprehensive biomechanics studies to serve as a basis for progressive refinement of design from the standpoint of accident injury hazard. Several presently employed methods for expressing the tolerance of the body to impact are described and attention is called to the need for refinement of these. Suggestions follow for long-range biomechanics studies in the areas of the head, neck, thorax, and abdomen, the results of which may be translated into improved criteria for predicting injury hazard.