The use of helmets is 37% effective in preventing motorcycle rider deaths — meaning that for every 100 unhelmeted deaths, helmets could have saved 37 lives.
Besides the District of Columbia, there are 47 states with a law that requires all riders or younger riders to wear helmets when operating a motorcycle. Fifty-seven percent of motorcyclist fatalities involved an unhelmeted driver in states withithout universal helmet laws, while states with universal helmet laws recorded 11%.