Mississippi Code Title 63. Motor Vehicles and Traffic Regulations § 63-31-3

(b) No person may operate any off-road vehicle upon any public property in this state unless each person under sixteen (16) years of age who is operating or riding on the off-road vehicle is wearing a crash helmet that complies with minimum guidelines established by the National Highway Traffic Safety Administration pursuant to the federal Motor Vehicle Safety Standard No. 218 (49 CFR 571.218) for helmets designed for use by motorcyclists.

(a) “Off-road vehicle” means any all-terrain vehicle, dirt bike or recreational off-highway vehicle. The term “off-road vehicle” shall not include electric bicycles.

(b) “All-terrain vehicle” or “ATV” means any motorized vehicle manufactured and designed exclusively for off-road use that is fifty-five (55) inches or less in width; has an unladen dry weight of one thousand (1,000) pounds or less; and travels on three (3), four (4) or more nonhighway tires. The term “all-terrain vehicle” shall not include electric bicycles.

(c) “Dirt bike” means a motor-powered vehicle possessing two (2) or more tires, designed to travel over any terrain and capable of travelling off of paved roads, whether or not the vehicle may be operated legally on a public street. The term “dirt bike” shall not include electric bicycles.

(d) “Recreational off-highway vehicle” means any motorized vehicle manufactured and designed exclusively for off-road use that is seventy-five (75) inches or less in width; has an unladen dry weight of three thousand five hundred (3,500) pounds or less; and travels on four (4) or more nonhighway tires.