Abstract: The invention environment is a conventional electrically powered railroad locomotive wherein a main generator powers the underlying traction wheels and wherein an auxiliary generator powers low-voltage locomotive components (such as alarms, wheels directional and acceleration control, etc.) through longitudinally extending electrical circuitry terminating at one or more multi-pins receptacles. The locomotive safety device of the present invention takes the form of a multi-perforate plug removably engageable with selected pins of a locomotive multi-pins receptacle and having internal circuitry tending to enforce the perilous "blue flag" condition of a stopped locomotive, such enforcement including the steps of initially warning the would be operator that the "blue flag" condition exists and thereafter making it practically impossible for such warned operator to initiate locomotive movement.