The size of the motor is usually 49cc, much smaller than most motorcycle motors. Because of the small motor, mopeds usually can not go faster than 50 kph (30 mph). Mopeds use less fuel than motorcycles, but some people complain that mopeds create more air pollution than motorcycles. Most of the time, you need a special license to ride a motorcycle but you only need an ordinary driver's license to ride a moped. It is usually illegal to ride a moped without a helmet.