What must occur before starting train movement in MATC mode?

In MATC (Manual Train Control) mode, it is crucial for the train engineer to depress the ATC Start button after securing the doors before initiating train movement. This step is essential as it activates the Automatic Train Control (ATC) system, ensuring that the train is ready to operate under automatic safety mechanisms. By securing the doors, the engineer confirms that all safety protocols concerning passenger safety and readiness for movement are met.

This process is designed to prevent accidental movement of the train and ensure that the system is engaged officially, which is critical in maintaining operational safety standards. Without this action, the train cannot be considered prepared for safe operations, regardless of other conditions, such as whether signals are clear or passengers are seated. This emphasis on securing the ATC Start button ensures that safety protocols are rigorously followed before any train movement can begin.