[(2) As used in this section, the term "all-terrain vehicle" means any motorized off-highway vehicle 50 inches or less in width, having a dry weight of 900 pounds or less, designed to travel on three or more low-pressure tires, having a seat designed to be straddled by the operator and handlebars for steering control, and intended for use by a single operator with no passenger.]

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http://www.fl-dof.com/forest_recreation/ohv_laws.html

Section 316.2074
F.S. All-terrain vehicles
(1) It is the intent of the Legislature through the adoption of this section to provide safety protection for minors while operating an all-terrain vehicle in this state.

(2) As used in this section, the term "all-terrain vehicle" means any motorized off-highway vehicle 50 inches or less in width, having a dry weight of 900 pounds or less, designed to travel on three or more low-pressure tires, having a seat designed to be straddled by the operator and handlebars for steering control, and intended for use by a single operator with no passenger.

(3) No person under 16 years of age shall operate, ride, or be otherwise propelled on an all-terrain vehicle unless the person wears a safety helmet meeting United States Department of Transportation standards and eye protection.

(4) If a crash results in the death of any person or in the injury of any person which results in treatment of the person by a physician, the operator of each all-terrain vehicle involved in the crash shall give notice of the crash pursuant to s. 316.066.

(5) Except as provided in this section, an all-terrain vehicle may not be operated upon the public roads, streets, or highways of this state, except as otherwise permitted by the managing state or federal agency.

(6) An all-terrain vehicle having four wheels may be used by police officers on public beaches designated as public roadways for the purpose of enforcing the traffic laws of the state. All-terrain vehicles may also be used by the police to travel on public roadways within 5 miles of beach access only when getting to and from the beach.

(7) An all-terrain vehicle having four wheels may be used by law enforcement officers on public roads within public lands while in the course and scope of their duties.

( A violation of this section is a non-criminal traffic infraction, punishable as a non-moving violation as provided in chapter 318.