helical worm gearmotor can achieves peak efficiency

helical worm gearmotor does not strictly require the presence of a clutch. Nevertheless, in some vehicles (e.g. motorcycles), a centrifugal clutch is added[2] to facilitate a "neutral" stance, which is useful when idling or manually reversing into a parking space.
In low-mass low-torque applications (such as motor scooters) a belt-driven gear reduction motor also offers ease of use and mechanical simplicity.