The main idea of "Bicycle Safety" is Helmets should always be worn when biking.
In "Bicycle Safety", by the National Highway Traffic Safety Administration, there is an overview that tells factual information about the number of deaths that occurred in the previous year. Then tells bicycle riders to always wore a helmet in order to avoid head injuries if an accident occurs. Buy a helmet, fit it, and wear it every ride. Instructions are clear and very easy to understand.