Drive unit for a rail-road vehicle

A vehicle for construction and maintenance work along a railway, the vehicle comprising:

• a lower part and an upper part which is rotatable in relation to the lower part and which comprises a working arm, the lower part including at least four rail-contact wheels configured to be in driving contact with rails, and at least one of crawlers and ground-contact wheels configured to be in driving contact with the ground outside the rails, the vehicle having first and second states of operation, the first state being with the rail-contact wheels in driving contact with the rails and the at least one of the crawlers and the ground-contact wheels out of contact with the ground, and the second state being with the rail-contact wheels out of contact with the rails and the at least one of the crawlers and the ground-contact wheels in driving contact with the ground;
• each drivingly connected to one of the rail-contact wheels for movement on the rails;
• wherein the hydraulic motors drivingly connected to the rail-contact wheels situated on one side of a longitudinal central axis of the vehicle are connected in parallel via a pair of lines that have ends connected to the hydraulic motors on the one side of the longitudinal central axis, for enabling the vehicle to move forward and backward;
• wherein the hydraulic motors on each side of the longitudinal central axis of the vehicle are connected in separate hydraulic circuit;
• and
• wherein each separate hydraulic circuit comprises a separate hydraulic pump.