Read the following closely, because it clearly indicates that most (75%) of the people killed in an ATV accident in this study group were not wearing helmets, but that only 25% of those would have lived if they had been wearing a helmet. Thus if 100 people were killed, 75 were not wearing helmets and only 19 would have lived if they had been wearing the helmet. In ALL of the other cases the helmet would make no difference. Thus, there is no fault at all in the 25 cases where the riders were wearing helmets or in the 56 cases where they would have died in any case, which is 81% of the cases in this study.
http://www.osha.gov/dts/shib/shib080306.html
Personal Protective Equipment
Personal protective equipment is strongly recommended when operating ATVs. The potential rollover hazards require the use of a DOT-approved helmet. According to a study of recreational ATV-related deaths in West Virginia, 65 percent of the deaths resulted from head and neck injuries. Of these fatalities, three-quarters of the ATV users were not wearing a helmet at the time of the incident [1].
CSPC indicates that 25 percent of those who died from head injuries sustained in recreational ATV accidents would have lived if they had been wearing a proper helmet [5]. In addition to helmets, appropriate boots, gloves, and goggles should also be worn.