Abstract: The present invention features a safety device that activates the air-brake system immediately upon the detection and/or occurrence of a railroad car derailment condition. The safety device includes a bar entension disposed beneath each car of a train. The extension bar is disposed transverse to the parallel rails and is positioned a few (approximately four) inches above them. When any one of the cars is caused to derail, the extension bar contacts the rail, causing a trip valve in the air-brake line to open. The opening of the trip valve gradually releases the air pressure in the line, thus automatically and instantaneously actuating the air-brake system throughout the train. The gradual release of the air pressure in the air-brake system provides more time for the engineer of the train to bring the train under control and reduces the possibility of damage and injury caused by the derailment.