What is the immediate action if the headlights fail enroute?

When the headlights fail while en route, substituting a white light for the headlight is the appropriate immediate action. This procedure ensures that the train can still signal its presence and maintain visibility in low-light conditions, thereby enhancing safety for both the train's crew and any oncoming trains or vehicles. Using a white light allows the train to continue its journey without stopping, ensuring that operations remain consistent while also adhering to safety protocols. This action is especially crucial in maintaining communication with other rail traffic and managing the overall flow of train operations.

Other choices may not effectively address the immediate safety concerns associated with a headlight failure. For example, informing the next station, while important, does not provide a solution for currently operating conditions. Stopping the train until repairs are made would disrupt service and compromise schedules, while increasing the train's speed would exacerbate the risks associated with operating without proper visibility aids. Thus, the substitution of a white light effectively meets safety requirements while allowing for continued operation.