Much progress has been made in many countries during recent years in detailed research into road accidents. The analysis facilities used by research workers to describe in a common language the severity of injuries and the deformation the vehicles undergo are improving.

Assessment of the constraints to which the occupants of crashed vehicles are exposed is still too approximate, despite the fact that this is essential to interpret the progress achieved in the field of safety and to make decisions concerning the future.

The methods used to analyze and classify accidents must reside on unquestionable physical basis. This is why Renault and Peugeot have discarded the Equivalent Test Speed method, replacing it by the Speed Variation method (ΔV) and, more recently, analysis based on two parameters, namely the speed variation and the mean deceleration of the undistorted part of the vehicle.

Application of these methods to a sample of accidents representative of the French situation is presented and discussed in the light of the severity of the lesions observed.