A self-driving work vehicle includes: a front wheel unit; a rear wheel unit including a left rear wheel and a right rear wheel; a variable traveling power supply apparatus that supplies rotational drive power to the left rear wheel and the right rear wheel independently; a left operation implement movable along a first path to adjust a rate of the rotational drive power to be supplied to the left rear wheel from the variable traveling power supply apparatus; a right operation implement movable along a second path to adjust a rate of the rotational drive power to be supplied to the right rear wheel from the variable traveling power supply apparatus; a parking brake provided for the variable traveling power supply apparatus; and a controller configured or programmed to cause a parking brake operating module to operate the parking brake.

An electronic steering and control apparatus and related control methods for a pair of variable drive units. The variable drive units may be hydrostatic, continuously variable transmissions (CVTs), or other similar devices. The apparatus is shown in use with a vehicle that may include a mowing deck.

When a second member of a power plant is in a first position with respect to a first member, a first communication port communicates with a fluid pressure supply source and second and third communication ports communicate with first and second pressure chambers of a fluid pressure motor. The second and third communication ports are shut off from a fourth communication port connected to a reservoir. Different positions of the second member result different communication and shut off relationships among the first to fourth ports. The first to fourth communication ports are provided in a plurality of communication port groups each formed by the first to fourth communication ports.

A bulldozer includes a control unit for controlling left and right steering clutches and left and right steering brakes, thereby executing a turning control of the vehicle. The control unit switches between a clutch control and a brake control on the basis of a differential between an actual turning radius and a target turning radius.

In a crawler type work machine, when switching from a pivot turning mode to a straight travel mode or a slow turning mode, a controller is configured to maintain a rotation speed of the turning motor until after a first timing at which the inside steering clutch begins partial engagement.