The present invention relates to a combined steering system for articulated tractors, comprising a steering gear (16), an articulated steering mechanism (18), a front-wheel steering mechanism (19) and a hydraulic apparatus for controlling an articulation steering mode or a front-wheel steering mode, further it is provided by a hydraulic articulation interlock (17) open in the articulation steering mode and closed in the front-wheel steering mode, wherein the articulation interlock (17) has an articulation locking ring (11) with interlock head seats (14) as well as interlock cylinders (12) containing an interlock head (13).
