A moped (// MOH-ped) is a type of low-powered motorcycle designed to provide economical and relatively safe transport with minimal licensing requirements.
Mopeds were once all equipped with bicycle-like pedals (the source of the term, motor + pedal), but moped has been increasingly applied by governments to vehicles without pedals, based on their restricted engine displacement, speed, and/or power output. Mopeds occasionally resemble powered bicycles, but most are now step-through designs (of both kinds, having either large or small wheels) and step-over designs similar to a regular motorcycle. Although mopeds usually have two wheels, in some jurisdictions low-powered three- or four-wheeled vehicles are also classified as mopeds.
A single-track vehicle is a vehicle that leaves a single ground track as it moves forward. Single-track vehicles usually have little or no lateral stability when stationary but develop it when moving forward or controlled. In the case of wheeled vehicles, the track of the front and rear wheel usually follow slightly different paths when turning or when out of alignment.
Single-track vehicles have unique dynamics that, in the case of wheeled vehicles, are discussed at length in bicycle and motorcycle dynamics, that usually require leaning into a turn, and that usually include countersteering. Single-track vehicles can roll on wheels, slide, float, or hydroplane.