Anyone under the age of 18 years must wear a helmet if they are riding a bike, even if they are a passenger on the bike. An adult is not required by law to wear a helmet while riding a bike. Additionally, a parent or guardian cannot allow a person under 18 years old to ride a bike without properly wearing a helmet. And a person cannot operate a bicycle with a passenger who is less than 18 years old unless that passenger is properly wearing a helmet. Last Reviewed: June 2019