Vehicle aggressivity is a measure of the degree to which a vehicle injury is inflicted upon the occupants of the other vehicles with which it crashes. During the last decade several methods of vehicle aggressivity rating were developed and applied in different countries. The question arises about the theoretical differences between the models and which is the most satisfactory vehicle aggressivity rating method. The aim of this paper is the theoretical analysis of the mathematical foundations of the existing aggressivity models and their comparison with regards to their ability to ‘rate’ vehicle models in terms of their aggressivity performance in two-vehicle crashes. Four vehicle aggressivity rating methods are described and compared, namely the Tl2L method, the MUARC method, the Oulu method and the modified Folksam method.