What is indicated by the DOOR SYSTEMS fault light?

The DOOR SYSTEMS fault light being illuminated indicates that there is a problem with the door control mechanisms in the system, which may be due to a defective door control unit. This fault light serves as a warning that the doors may not be functioning properly, which is critical for the safety and operation of the train. A defective door control unit could lead to doors that do not open or close as intended, potentially creating hazardous situations for passengers.

Understanding how the door systems operate is essential for safe train operations. The door control unit is responsible for managing the opening and closing of train doors, ensuring that they function correctly in tandem with safety protocols. If this unit fails, it directly impacts the train’s ability to allow passengers to board or disembark safely.

The other options listed relate to different systems and conditions that are not specifically tied to the door control unit. For instance, the status of the brakes, air pressure, or traction motors pertains to different operational aspects of the train, and thus they do not directly correlate with the DOOR SYSTEMS fault light.