motorcycle, motor vehicle whose design is based on the bicycle. The German inventor Gottlieb Daimler is generally credited with building the first practical motorcycle in 1885. The motorcycle did not become dependable and popular, however, until after 1900. The typical motorcycle has an air-cooled engine supported in a metal frame between two wheels. Sometimes a third wheel is added to support an open carriage, called a sidecar, which is attached to the motorcycle. The motor is a two- or four-cycle gasoline engine with one to four cylinders. Its piston displacement generally ranges from 50 to 1,500 cc. Although the motorcycle is not as safe a vehicle as the automobile, its convenience and economy have made it very popular; it is widely used for pleasure riding, racing, and commercial transportation of light goods. Modern touring motorcycles provide automatic transmission, stereo sound, and luggage space. Motorcycles are widely used by the police for traffic patrols. Use of the motorcycle has increased greatly in recent years as a result of the development of the inexpensive, lightweight motorcycle, manufactured chiefly in Asia. Dirt bikes, motorcycles specially designed and outfitted for off-road use, are also now common. The motor scooter, a variation on the motorcycle, has smaller wheels and has most of its working parts enclosed by a shield. The driver sits on a seat with his or her feet on a wide metal platform behind the front shield. Another variation on the motorcycle is the moped, a bicycle to which a small (under 50 cc) auxiliary engine has been attached. Motorcycle racing is done both on paved and unpaved surfaces, over closed and cross-country courses, for a variety of vehicle classes. Particularly popular is motocross, in which dirt bikes are raced over an off-road closed course with numerous turns, jumps, hills, and other irregular terrain.

Sport of running motorcycles on tracks, closed circuits, or natural terrain. The main types are (1) road racing, conducted on a course made up wholly or partly of public roads; (2) trials, conducted both on and off the highway; (3) speedway racing, conducted on a short, flat, oval dirt track; (4) drag racing, conducted on a straight quarter-mile strip of pavement; (5) hill climbs, conducted on a large dirt mound; and (6) motocross. The first international road race took place in Douran, France, in 1905. The most famous race is the Tourist Trophy, established on Britain's Isle of Man in 1907. Motorcycle racing in North America began in 1903; since 1937 the Daytona 200-mi (320-km) race has been the leading U.S. race.

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Bicycle or tricycle propelled by an internal combustion engine. The first motor tricycle was built in 1884 in England, and the first gasoline-engine motorcycle was built by Gottlieb Daimler in 1885. Motorcycles were widely used after 1910, especially by the armed forces in World War I. After 1950 a larger, heavier motorcycle was used mainly for touring and sport competitions. The moped, a light, low-speed motor bicycle that can also be pedaled, was developed mainly in Europe, and the sturdier Italian-made motor scooter also became popular for its economy.

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