In order to address the thoracic risk in frontal impact, a restraint system combining belt load limitation and pyrotechnic belt pretension, known as the Programmed Restraint System (PRS), has been fitted to Renault cars since 1995. This new load limiter was initially designed to limit forces to 6 kN. In this paper, 89 French accident cases, with Equivalent Energy Speeds (EES's) from 40 to 80 km/h and involving frontal collisions with cars equipped with PRS, are reported. The purpose of the study, based on this accident file and on another accident file with textile limiters, is to establish, for belted occupants, the thoracic injury risk as a function of occupant age and load applied at the shoulder level. One observes that for 50% of thorax risk of Abbreviated Injury Scale (AIS) 3+, the force for all ages together is 6.9 kN. These results are obtained for 256 occupants. The shoulder belt load appears to be in accordance with the occurrence of chest injuries. The paper also includes a comparison of results obtained in real-world accidents with 209 Heidelberg cadaver tests, and a relationship between the Hybrid III thoracic injury measurements and the shoulder belt load. The study confirms that a 6 kN force level is not sufficient to protect a larger proportion of the population. A belt load limitation of 4 kN, combined with a specifically design airbag, would make it possible to protect 95% of those involved in frontal impacts from AIS 3+ thorax injuries.
Abstract