A working machine includes a body, a ground engaging structure including at least one pair of driven wheels, an engine, and a transmission for transmitting power from the engine to the driven wheels, a pressurized air system for providing pressurized air for use in applying service brakes for braking the wheels, the transmission including a transmission member which is rotatable with the wheels, a transmission brake for applying a braking force to the transmission member, and the transmission brake being releasable by a hydraulic fluid operated transmission brake releasing device, the hydraulic fluid for the brake releasing device being derived from a pressurized hydraulic fluid system which includes a hydraulic pump and one or more pressurized fluid operated services, there being a transmission brake control valve to control the flow of hydraulic fluid to the brake releasing device, the transmission brake control valve being actuated to permit pressurized hydraulic fluid to flow therethrough to release the transmission brake, by air pressure, derived from the pressurized air system.