Abstract: The doors of railroad passenger cars swing inward and toward the front of the car when opened for entry or exit by the passenger. An automatic locking device is described which may be mounted on the exterior surface of the door close to its trailing edge. When the railroad car is in motion, the pressure of the relative wind on an air foil acts to rotate the locking device to a position that prevents the door from opening. When the train slows and stops, the relative wind decreases and the locking mechanism returns to it's original position permitting the door to be opened.