A rail vehicle braking system includes a service brake having a movable piston (8) which with a body (2) of the system delimits a service brake chamber (13) supplied by a first source, a piston rod (21) disposed in that chamber and fastened to a second side (32) of the piston turned towards that chamber, and a parking brake (7) disposed in the body and including a blocking device (20) disposed in that chamber and movable to act on the rod, and a movable actuating device (23, 24) which with the body delimits a parking brake pressure chamber (25) supplied by a second source; the blocking and actuating devices being configured to immobilize/unblock the rod so as to block/unblock the piston in a position.