Yes, according to the regulations of Little Sahara State Park in Oklahoma, all riders and passengers of ATVs and other off-road vehicles are required to wear a helmet at all times while on the sand dunes. This includes all types of off-road vehicles, such as ATVs, dirt bikes, and dune buggies. Wearing a helmet is important for your safety while enjoying the activities at the park. It is always a good idea to bring your own helmet to ensure proper fit and protection, but helmets are also available for rent at the park.  Additionally, it's important to follow all other park rules and regulations for your safety and enjoyment and to help preserve the park's natural beauty and resources.