Abstract: A pedal-operated vehicle including a frame, at least two supporting wheels, a driven wheel hub, and a variable ratio drive system comprising, (in one embodiment) a planetary gear set mounted adjacent and externally of the driven wheel hub. The gear set includes a single sun gear, a single ring gear, and at least one planet gear rotatably mounted on a carrier, with the sun gear being engageable with the wheel hub for driving the same. A foot-operated crank is drivingly connected to the planetary carrier, whereby torque generated by the crank is transferable to the planetary carrier. A rotation controlling means such as a brake is located externally of the ring gear and fixed to the frame for affecting the rotation which the ring gear is permitted to have as the planetary carrier is turned. A hand-operable control unit is used to adjust the brake's effectiveness, whereby the speed of rotation of the sun gear is a function of the rotation which the ring gear is permitted to have.