NHTSA defines the term motorcycle, for the purpose of the statute and regulations it administers, as a motor vehicle with motive power having a seat or saddle for the use of the rider and designed to travel on not more than three wheels in contact with ground” (49 CFR 571.3).

NHTSA defines the term motor driven cycle as a motorcycle with a motor that produces 5-brake horsepower or less. A motor driven cycle is exempted from certain requirements of the FMVSS that apply to motorcycles.

NHTSA does not define the terms motor scooter, moped, pocket bike, mini-chopper, mini-ninja, or any other terms of this nature that may be used for the purpose of marketing motorcycles and motor driven cycles. Those terms therefore have no relevance to the classification of a vehicle for the purpose of determining which FMVSS would apply to it. Note that States are free to regulate the use of such vehicles and may use their own terms when describing vehicle types for the purpose of their regulations.