Abstract: A human-powered wheeled vehicle has a wheeled frame, a seat for the rider of the vehicle, a pair of levers arranged for pivotal movement about a common axis, clutch means whereby movement of either of the levers in a first direction about the common axis is transmitted to the sprocket whereas movement of either of the levers in a direction opposite to said first direction is not transmitted to the sprocket, and sliders movable along slideways, the sliders being connected to the levers and the arrangement being such that, movement of the sliders serves to effect alternate pivotal movement of the levers.