When must a passenger train's illuminated marking device be tested?

The testing of a passenger train's illuminated marking device is crucial for safety and visibility on the tracks, especially in low-light conditions or at night. The correct answer is that this testing must occur before the train leaves its initial terminal. Conducting this test ensures that the device is functioning correctly from the very beginning of the train's journey, thereby helping to prevent incidents related to visibility and enhancing overall operational safety.

The other options suggest testing under conditions that would not guarantee uniform safety across the entire journey. Testing only during the evening shift would overlook the necessity of ensuring visibility at all times. Testing every three stations may lead to situations where the device could fail between tests, compromising safety at critical times. Similarly, relying solely on instructions from the Dispatcher to test this device could lead to inconsistencies and delays in safety checks. Therefore, the requirement to test before departure establishes a proactive and consistent approach to ensuring safety in train operations.