Bicycle helmets. Effective but underused.
Weiss
B D
BD
D000293:Adolescent; D001642:Bicycling / Q000293:injuries*; D002648:Child; D006259:Craniocerebral Trauma / Q000401:mortality / Q000517:prevention & control*; D006260:Head Protective Devices / Q000706:statistics & numerical data*; D006801:Humans