A scooter is a style of two-wheeled motor vehicle traditionally defined by characteristics such as a step-through frame, wheels less than 16" in diameter, and an engine located below the rider and to the rear. Though throughout the history of scooters, there have been models which challenged or defied this definition, incorporating elements or designs from motorcycles (distinguished by a tank between the rider and handlebars and an engine located beneath the rider and to the front of the vehicle) and mopeds (which have pedals), developments over the past 20 years have broadened the "scooter" label to include a wide array of vehicles and designs featuring many different technologies and capabilities. Modern scooters cover a broad spectrum of designs: step-through or step-over frames, small or large wheels, front fairings or floor boards, and manual or automatic transmissions.

At one end of the current market, the Vespa LX series reflects the scooters' historical antecedents: small wheels, floor boards, front fairing, inner fairing storage. At the other end, the Honda Big Ruckus features no bodywork, floorboards or step-through frame, but is still classified as a scooter due to its smaller wheels and engine placement. The Piaggio MP3, with two front wheels (three wheels total) reflects the fluid nature of the scooter classification. Modern scooters have a wide range of engine displacements, from under 50 cc to over 799 cc, and some have engine locations in stark contrast to classic scooter design (e.g. Yamaha T-Max 500, Suzuki Burgman 650, Gilera GP800).

Generally the term "scooter" is not defined in law, as laws are based on characteristics such as engine size and power, and maximum speed. The United States Department of Transportation defines a scooter as having a platform for the operator's feet or has integrated footrests, and has a step-through architecture. In the U.S. and Europe, scooters are classified by vehicle codes as either "motorcycles" or, for those with 50cc or smaller engines, "mopeds." Each are subject to the applicable laws for their categorization.

Description

Unlike most motorcycles, scooters usually feature bodywork, including a front leg shield and body that conceals all or most of the mechanicals. There is often some integral storage space, either under the seat, built into the front leg shield, or both. Most modern motor scooters have smaller wheels than motorcycles, 12 to 15 inches (30 to 37.5 cm) in diameter, although maxi- and big-wheel scooters may have larger wheels. Most scooters have smaller engines than motorcycles, 50 cc to 400 cc with a single cylinder, although larger models have twin cylinder 400 to 800 cc. motors.