Requirements on chin protection in full-face helmets for motorcyclist impact and injury situations.

Helmets with integrated chin protection are currently the most widespread helmet design in Europe. Helmet design is extensively prescribed by design and performance regulations. An evaluation of the Japanese, American and European regulations proves that this is not the case for chin protection. Results from investigations between 1984 and 1991 show the development tendencies for the protection of the head in the chin area. The measurement methods used in the investigations enabled the parallel measurement of chin forces, chin strap forces and head deceleration in a simulated impact in the chin area. The results give the first information on the combined effects of the padding of the chin section, the geometry of the chin section and chin strap attachment and the effects on load distribution in the case of an impact on the chin section. Most of the test regulations do not consider the chin region. This study analyses impact situations in real accidents. The impact situation of 598 analyzed crash helmets reveals that only 57.7% of all impact points are situated within the protection region defined by ECE, 14.1% in the marginal region and 28.2% clearly outside this region. The highest percentage of impacts occurs in the chin region, with predominantly flat impact patterns. The so-called 'turn' is not confirmed in accident reality. The most frequent impact for the chin region is the impact measured 4 to 6 cm 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 skull, and on the other hand a more sagittal right-angular effecting force, causing fractures to the lower jaw as well as extensive facial fractures. The fracture of the skull base appears to be a frequent side effect. In an oblique 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 framework conditions, the optimum helmet tests can be defined by this analysis.