EUGENE — A lawmaker from Eugene plans to introduce a bill that would require all bicyclists to wear a helmet.

With high gas prices and environmental concerns pushing more people to two-wheeled transportation, State Sen. Floyd Prozanski, a longtime bicycling advocate, says it’s time to ensure better safety.

Approved 15 years ago, Oregon’s current helmet law only requires riders younger than 17 to wear one. The fine for riding without a helmet is $25.

Several U.S. cities require adults to wear bicycle helmets. But if Prozanski’s plan succeeds, Oregon would be the first state to have an all-ages helmet law.

The Web site BikePortland .org was first to report that Prozanski planned to introduce the helmet bill in the 2009 Legislature. The state’s largest bicycle advocacy group, the Bicycle Transportation Alliance, isn’t waiting until then to oppose it.

An alliance spokesman said the group fears that requiring helmet use on public streets could decrease ridership because adults who don’t want to wear one might choose another mode of travel.

“We support and encourage helmet use,” spokesman Karl Rohde said. “But we do not think a law is the right way to approach it.”

Prozanski, meanwhile, said he doesn’t think a helmet law will stop people from riding bicycles: “I have a real hard time with that one.”