As with DOT, the impact severity is described in terms of the impact velocity. The single impact approaches the M2000 first impact levels and actually exceeds it for the large size headform. However, the second impacts required in M2000 and DOT may actually require helmets with greater protective capacities. Regulation 22 also uses variable weight headforms, essentially the same EN headforms used in the current European Norms. The table also describes coverage requirements.
Helmets protect by interposing between the head and the blow.
All three standards describe where test impacts may be applied to the helmet in terms of the geometry of the headform. M2000 and DOT describe test lines which bound a portion of the helmet surface. Test impacts must be centered on or within these test lines. Regulation 22 revision 4 describes three impact sites and a locus into which a fourth impact is delivered. The critical issue of coverage is a matter of just how low on the surface of the helmet an impact can be applied.