Technical Demands on Safety in the Design of Crash Helmets for Biomechanical Analysis of Real Accident Situations 912911
Crash helmets for motorcyclists are subject to certain test specifications by national and international reglements. For the European community the ECE-R 22 is valid, in America the tests are made according to SNELL as well as FMVSS 218. In all test procedures the protruding stability, the form stability of the carrier device and the shock absorption is tested. This study investigate impact situations in real accidents. The impact situation of 598 analysed crash helmets reveals that only 57.5% of all impact points are situated within the protection region of helmets defined by ECE, 14.1% in the marginal region and 28.2% clearly outside this protected region. The highest percentage of impacts occurres in the chin region, which is not taken into consideration in test definitions ECE as well as FMVSS. The so-called ‘double-impact’, which is a base of test procedures and induce therefore, is not confirmed in accident reality. The most frequent impact for the chin region is an impact placed 4 to 6cm away from the middle of the chin-bar. Biomechanically regarded, two typical force directions were defined, on the one hand oblique from below, with subsequent injuries to the lower jaw and other indirect injuries to the top of the scull, and on the other hand a more sagittal rectangular force direction, causing fractures to the lower jaw as well as extensive facial fractures. The fracture of the scull base appears to be a frequent secondary effect. In an oblique force direction from below it is valuated as an indirect injury, in a rectangular impact, however, it is regarded as a direct injury. Within the respective frame- work of this study, optimum helmet test conditions can be defined by this analysis.