The undergoing research establishes human head tolerance limits against impact. The methodology consists in a finite element modeling of 64 accidents of helmeted motorcyclists and American footballers, and pedestrians. The finite element model of the head of the University of Strasbourg is controlled with the kinematics, derived from a HYBRID III dummy head and an analytical model of the pedestrian, sustained by each victim. A statistical correlation study between the calculated head loadings and the observed injuries leads to the identification of injury criteria thanks to risk curves. A global strain energy of the subarachnoidal space of 5.4 J leads to subdural or subarachnoidal haematoma. A brain Von Mises stress of 18 kPa generates moderate neurological lesions which become severe from 38 kPa. A global strain energy of the skull of 2.2 J leads to skull fractures which are besides well predicted by the model.