This study aims at determining, with the maximum precision, the performance of the 3 point safety belt in different accident configurations, and more particularly in frontal collisions.

For this purpose, two matched samples were taken from a file of 3000 accidents, analysed by a multidisciplinary study group. These samples of 100 front seat occupants wearing seat belts, and 100 not wearing seat belts were made up in such a manner that, for every belted occupant, corresponds an occupant not wearing a belt, the one and the other being in equivalent circumstances, using the following factors:​

• Make and type of the vehicle
• Seat occupied
• Age (as far as possible)
• Direction of impact
• Violence of the impact (same class of ▵V and mean γ)
• Possible intrusion of passenger compartment
• Possible overload caused by a rear seat occupant

Using this method of comparison, one can appreciate the effectiveness of the 3 point belt and explain the variations of effectiveness that appear in normal case studies.