This guide is for general information only and is not legal advice. Laws change — verify current rules with your state DOT or a licensed attorney before relying on this for any legal matter. Read full disclaimer.
Oregon requires a bicycle helmet for any rider under the age of 16. The same rule extends to children carried as passengers in a child seat or trailer. ORS 814.485 makes it a Class D traffic violation for a person under 16 to operate or ride a bicycle on a public way without an approved helmet. The presumptive fine is $25. Parents and guardians can also be cited under ORS 814.486 for knowingly permitting an unhelmeted child to ride. See ORS 814.485 (Failure to wear protective headgear).
If you're 16 or older, Oregon doesn't require you to wear a helmet by state law. Riders under 16 (and any child carried as a passenger) must wear a helmet that meets the CPSC standard.
Cities can be stricter than the state floor, and bike-share systems often require helmets regardless of age. If you're renting or commuting in a major city, confirm the local rule before you ride.