A person must be six years-old or older to operate an ATV on public land in New Mexico. A person under 10 cannot operate an ATV with an engine size greater than 100cc. For people between the ages of 10 and 18, a person over the age of 18 with a valid driver's license must be present. All riders under the age of 18, no matter if they hold a motorcycle license ordriver's license, must have a safety permit to drive an ATV.
Check out these Los Alamos, NM ATV/OHV resources:
