A method of regulating a travelling speed of an agricultural machine includes providing a diesel engine to drive a variable displacement pump, the variable displacement pump connected by a hydraulic line to at least one hydraulic motor connected to a running gear so as to drive the agricultural machine at the travelling speed. The method further includes measuring a speed of the diesel engine, and providing a delivery volume from the variable displacement pump via the hydraulic line to the at least one hydraulic motor in proportion to the measured speed of the diesel engine, where a speed of the at least one hydraulic motor controls the travelling speed of the agricultural machine.