An operator-propelled, four-wheel vehicle uses a treadmill to drive two rear wheels through a bicycle type derailleur and sprocket gear shifter which provides gear changing capability. The front wheels, each of which have disk brakes, are steered by an automotive type steering apparatus. A vertical extension from the steering mechanism at the front of the vehicle mounts a horizontal steering bar to provide steering control. The steering bar also mounts control grips and cables for the front disk brakes and clutch assembly, as well as the gear shifter. An automatic breaking system ensures that an unmanned vehicle will remain in place.