If you can’t remember how a bike helmet should fit, just remember: ears, eyes and mouth.

Ears: The arch on the side of the helmet should form an invisible “V” around your ear.

Eyes: When you look up, you should see be able to see the front rim of the helmet.

Mouth: When you open your mouth, you should feel the helmet’s chin strap tighten around your jaw.

This is just one of many helpful bits of advice Joyce Mahoney, a member of the Volunteer Bike Patrol in Acadia National Park, readily supplies to fellow cyclists.

The patrol, which has served on and off since the 1990s, is back this summer to assist National Park Service rangers out on Acadia’s carriage roads.

The carriage roads, designed and financed by John D. Rockefeller Jr. in the early 20th century, are 45 miles of motor vehicle-free gravel roads winding through Acadia. As the name suggests, they were originally built for horse-drawn carriages, but are now used for hikers, bikers and horseback riders.

Acadia rangers make rounds on bikes, but are often called away to other park duties or incidents.

The volunteers provide service on the trail to help the rangers out. The 16 members are required to work two hours per week each, but most do more.

Sporting royal blue polo shirts with their name embroidered in white on the right and a National Park Service Volunteer patch sewn on the left, they bike popular carriage trail routes, stopping to assist anyone who looks lost or remind visitors of courtesy rules.

“It basically means helping the visitor have the best time while they’re out in the park. It might be providing maps, giving directions. If they run out of water, we carry spare water bottles to give them so they don’t get dehydrated and overheat,” National Park Service ranger Josh Bennoch explained.

Bennoch, a Bar Harbor native, oversees the Volunteer Bike Patrol. A graduate of the University of Maine at Orono with a degree in park, recreation and tourism management, the 14-year veteran of the National Park Service is well aware of the issues that often arise.

“Visitors are not really aware of what the courtesy rules are, so they’ll drop bicycles in the middle of the carriage roads and go take pictures and not realize the safety hazard they’ve created,” Bennoch said. “The volunteers will come along and address those kinds of issues to make things a little safer.”

And they have fun doing it, too. After addressing an issue with a visitor, the conversation often flows in to a friendly chat about the area.

“We’re not here to reprimand people or make them angry — we just want them to have a good experience,” Mahoney said.

Mahoney and her husband, Jim, recently moved to Bar Harbor from Berlin, Conn. Joyce is the assistant librarian at Mount Desert Island High School, while Jim continues to do his work in economic development remotely for the city of Berlin.

The Mahoneys enjoy being part of the bike patrol because they feel it is a simple way to give back the island community that has welcomed them “with open arms in every way possible.”