The biofidelity of the injury criteria of the European standard for motorcycle helmets (ECE Regulation No. 22, Section 7.3 Impact-absorption tests), were examined against biomechanically based injury metrics. Using a method to measure the helmet contact pressure on the headform during impact, twenty helmets were dropped according to ECE R22 free drop specifications. A total of 76 impacts to the front, crown, rear, right and left side of the helmet were examined using finite element simulations to predict skull fracture. The ECE R22 criteria, peak head acceleration and HIC, were correlated with these injury metrics.

It was found that ECE R22 criterion of peak headform acceleration is the best correlate with all injuries. HIC was an acceptable correlate for brain injury metrics but a very poor correlate to skull strain. The current peak headform acceleration limit of 275 g resulted in a 20% probability of skull fracture.

This research has shown that peak head acceleration can be an acceptable injury metric for skull fracture using the ECE R22 test method. The current ECE R22 linear acceleration limit of 275 g is slightly higher than the calculated thresholds of injury used in this study for skull fracture, 252 g for 15% probability of skull fracture. Even though a free head drop method was used, the resultant translational acceleration trace at the center of gravity of the headform proved no better at predicting concussion than the rigidly mounted FMVSS No. 218 headform. When headform rotation was measured and used in the SIMon analysis, an increase in the concussion injury metric was seen. In order to use SIMon as a brain injury analysis tool, unconstrained free drops with headforms instrumented to record angular motion are necessary.

A comparison of test results for helmets which were tested using both FMVSS No. 218 and ECE R22 methods was conducted. It was found that the peak head acceleration was an acceptable injury metric for skull fracture in both studies. Although FMVSS No. 218 and ECE R22 test protocols are different, both have a pass/fail criterion based on the peak head acceleration. Since peak head acceleration correlates to skull fracture, any future modification of the peak head acceleration criterion can be based on acceptable probability of skull fracture analysis.