Abstract: A dual hydraulic steering system for a vehicle has two steering circuits each having a pump and a steering valve unit. A first circuit is connected to the main working spaces of the double-acting steering cylinders while the second circuit is connected to the piston rod spaces of the cylinders. The first circuit has an engine driven pump while the second circuit has a ground wheel driven pump and an accumulator. Both circuits are connected to a common tank which is divided below a lowest normal oil level. Pressure switches and electromagnetic valves feed flow from the first circuit to the second in case of low pressure therein. This cross-over is prevented when a level switch detects low tank oil level.