21.4 Bike riding. In 2012, the National Highway Traffic Safety Administration (NHTSA) of the U.S. Department of Transportation conducted the National Survey of Bicyclist and Pedestrian Attitudes and Behaviors. A total of 7509 individuals aged 16 years and older participated in this survey. Of these 7509 individuals, 2580 individuals reported that they rode a bicycle within the past year. Of these self-reported bicycle riders, 1187 said they had never worn a helmet when riding a bicycle. Based on this information, we know the sample proportion, , of bicycle riders from this survey who have never worn a helmet is