Helmet use, helmet use laws, and motorcyclist fatalities.
D000063:Accidents, Traffic; D006259:Craniocerebral Trauma / Q000401:mortality; D006260:Head Protective Devices; D006801:Humans; D007878:Legislation as Topic; D011482:Protective Devices; D013223:Statistics as Topic; D014481:United States; D014947:Wounds and Injuries / Q000401:mortality*