Helmets work best.
Graitcer
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D000063:Accidents, Traffic / Q000517:prevention & control* / Q000706:statistics & numerical data*; D001642:Bicycling / Q000293:injuries* / Q000331:legislation & jurisprudence; D003299:Cooperative Behavior; D006260:Head Protective Devices; D006801:Humans; D014481:United States