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No method based on experiments is convenient for evaluating globally the potential risk of a given vehicle for the whole population of pedestrians at risk, which encompasses the smallest children and the tallest adults simultaneously, when a large range of impact speeds has to be considered. Mathematical models are also inadequate, due to the large number of runs required for obtaining the probability of impact on each section of the front end profile. This paper describes first a recently improved mathematical method for defining the head trajectories yielded by experimental simulations or by a validated mathematical model. Then, a computer program is presented that simultaneously uses this method and statistical data concerning real accidents. The output of this program is a distribution of the impact probabilities for a given profile. The head impact velocities can be utilized for weighing the results. Possible improvements and application of this method are discussed.

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 paper is related to the pedestrians struck by a vehicle. From the results of multiple runs performed with a previously validated mathematical model, an equation is defined which describes the trajectories of their heads. When the distribution in heights of the pedestrians and the distribution in speeds of the colliding vehicles are taken into account, this equation enables the prediction of the head impact probability for the sundry areas of the front end of the vehicle, according to its profile.

Car-pedestrian accidents were selected with reference to criteria like relevance in terms of injury severities representativity and reproducibility aiming to as accurate as possible reconstructions by dummy and cadaver tests. Parameters necessary for performance of these reconstructions were evaluated from the data of accident investigation teams. Preliminary tests were performed by research departments of automobile manufacturers to check the estimated conditions of these accidents before performing their reconstructions. A particular aim was to obtain insights into the mechanisms leading to injuries in pedestrian accidents; more generally reconstructing actual accidents is a privilegied approach to determine human tolerance limits and the corresponding protection criteria on dummies; the injuries resulting from the actual accidents are consequently compared with the data measured on dummies and cadavers in the reconstruction experiments.

A large number of experiments involving cadavers - including real-world-accident reconstructions - have been performed for the purpose of enhancing the state of knowledge concerning tolerance levels and protection criteria relevant to side-impact conditions. However, the scatter of the findings, as well as the considerable differences in injury severity levels (differences that cannot be accounted for by age differences alone) have limited the conclusions that it was possible to draw from these investigations in terms of criteria, mainly concerning thoracic protection. The major cause of scatter is the considerable differences in skeleton quality between subjects. Analysis of the rib characterization test findings made it possible to define a thoracic resistance index enabling the establishment of a classification of subjects. This index, which was validated with our sample, allowed us to evaluate the pertinence of the various side-impact protection criteria considered.

The 3-point static belts that are installed in Renault and Peugeot vehicles are equipped with a force limiter near the upper anchorage. This system is made up of several bands of textiles that tear successively for the increasing levels of force exerted by the occupant. One can thus associate, for each person in the accident, the degree of the thoracic AIS and the value of the support force, expressed in daN. This relationship is established for 92 belted occupants who were involved in frontal impacts. In addition it is indicated which are the distributions of impact violence parameters incurred and which are the distributions of ages in order to determine the statistical meaning of the required results. The levels of tolerance observed in this sample are compared to thoracic injuries observed on belted cadavers exposed to equivalent violent impacts.

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.

THE FREQUENCY AND SEVERITY OF LESIONS SUSTAINED BY THE OCCUPANTS OF CARS IMPACTED LATERALLY depend upon the main following factors: impact localization, intrusion into passengers' compartment, car speed variation, direction of occupant trajectory, objects contacted by the various body areas. 296 lateral impacts are being described hereunder by means of factors below. Consequences are drawn therefrom as to the coming improvement of occupant protection taking account of the current state of the art in Biomechanics and automobile technique. IN COMPARISON WITH THE PROGRESS achieved with a view to improving occupant protection against frontal impact, the knowledge available on the lateral impact and the methods for reducing the severity thereof are very poor. In as much as the results achieved in biomechanics up to this date are known, there is still much to do in this field. Mc Elhaney (1)* already stressed the fact in 1971 after Snyder (2).

Collisions between vehicles and pedestrians are analyzed, in conjunction with a bidisciplinary “pedestrian” investigation, by simulating accidents using adult and child dummies. A series of experimental collisions were carried out at varying impact speeds with a sample of vehicles representative of the various front-end profiles of vehicles at present running on the roads, the purpose being to study how these profiles affect the kinematics of the adult and child and to define the risks of injury during the different phases of the accident. The degrees of severity of the impact against the vehicle and the ground are compared and head impact speeds analyzed. Countermeasures are proposed and an initial evaluation made using a cadaver.

This paper deals with frontal crash simulations with 3 point seat-belts, in which the conventional anthropomorphic test dummy has been replaced by a fresh unembalmed cadaver. Numerous test conditions have been used. Here are the complete results on the thorax for 31 cadavers in dynamic tests and 7 others in static tests. Specific interest in the thorax comes from the examination of injuries which has shown that, for a normal test, severe injuries are seldom located elsewhere than in the thorax. Methodology, which is the first described, states in particular how the cadavers are prepared with reconstitution of blood pressure and lung inflation and how skeleton strength is characterized. Among the results shown are those for the thorax autopsies, the corresponding seat belt restraint forces, some measurements with dummies used simultaneously and some data on recorded thorax deflections.

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.