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With drivers wearing 3-point seat belts, the head-steering-wheel impact occurs in most serious accidents, so inducing mainly face injuries. In a first part, the authors analyze the injuries observed in a sample of 1180 belted drivers involved in frontal collisions, making a distinction, mainly for facial impacts, between injuries related to the properly so-called face and those to the skull and brain and the different possible lesional correlations. In the second part are presented the results of work carried out in order to define a human face model adaptable to any type of Hybrid II or Hybrid III dummies' heads. The use of this model allows one to elaborate a new protection criterion for the face, destination of which should be to complete the head and skull protection criterion, such as the HIC (or another equivalent criterion which could possibly replace it).

Biomechanical studies related to the head have been mainly directed towards the determination of cerebral tolerance to impact in the absence of fracture. However, the frequency of skull trauma producing complex fractures and cerebral lesions linked to these fractures should be taken into consideration. On a human being, impacts under similar mechanical conditons can produce either fatal encephalic lesions without fractures or skull fractures with encephalic lesions if the subject has a different skull morphology. A sample of 146 subjects has been studied to determine the relation between the morphological characteristics of the skulls (weight of the skull cap, thickness, weight of the cranial skeleton…), their mineralization. The mechanical tests were performed on bone fragments (bending and shearing tests). Nine accelerometers were used during the experiments of various types of impacts. The results were computerized. The skull fractures observed (a total of 45) are described.

This report describes the results of 42 tests involving direct impacts on the head, performed on fresh, unembalmed, perfused cadavers, helmeted or not helmeted, by means of a free-fall procedure. Three main kinds of impact were investigated: frontal, temporal-parietal, and frontal-facial. The results yield a typology of lesions (associated with various test conditions) that differs from the one described in earlier, similar reports published by A.M. Nahum and R.L. Stalnaker. The measurements confirm a tolerance level of HIC>1500 in the case involving skull impacts under the conditions specified in the text.