The methods used at the Transport and Road Research Laboratory to determine tolerable loadings for car occupants in impacts are based on correlating injuries received by living human car occupants in accidents with measurements made on dummies or test devices suitable for research or approval testing in laboratory simulations of these accidents. Where suitable accident data exist a statistical technique is used which enables the proportion of the population at risk who will suffer injury at any given level of loading to be predicted. Predictions of the effect in terms of injury incidence to the population can be made for anv level of load limitation. These predictions may be used in forming regulations and to guide the design of vehicle systems, for example of occupant restraints. Three examples are discussed; the loadings produced by a safety belt, the knee/thigh/hip loading resulting from knee impact with the fascia and loadings on car occupants in side impacts.