A tractor has hydraulically driven wheels at a cab end and castor wheels at an engine end. It can be driven cab forward in a working mode with a header on the forward end. It is rotated to engine forward in the transport position for more stable higher speed travel. The driver's console is rotated in the cab with the steering and speed control elements moved with the seat for the driver to face forwards and its position is detected by switches. In the engine forward position for transportation, the control system detects the seat position and operates the controls for higher speed drive and to prevent operation of the header. The engine has a series of ratings which can be selected depending upon whether the header motor is engaged so that a highest engine speed is used only when the header is disengaged and the lower speed is used for higher fuel efficiency when the header is operating.