In order to reduce loads on occupants restrained by seat belts, it has become necessary to work on an optimized limitation of the restraining forces, while taking into account the broadest possible population, especially elderly people. A first step in this reduction was taken with the introduction of the first generation Programmed Restraint System (PRS) in the year 1995, with a seat belt force threshold of 6 kN; thirty-seven frontal accident cases involving this type of restraint were investigated. The corresponding data, crash severities and occupant injuries, are reported in this paper. Analysis of these data combined with the University of Heidelberg/National Highway Traffic Safety Administration study findings, shows that it is necessary to go a step further by reducing the shoulder belt force to 4 kN. As this objective cannot be achieved with a standard restraint system, it was necessary to redesign the airbag and its operating mode, that is, a new seat belt and airbag combination called PRS II. The paper summarizes the data obtained with the 6 kN load limiter restraint in real-world collisions. A description of the new system is given. Its performance in offset crash situation regarding a European standard belt and air bag system is discussed. The paper provides data on the validation of the PRS II in various frontal collisions and static out-of-position (OOP) tests. (A)
Abstract