What is the acceptable position of the ATC mode switch when leaving the cab?

The correct position of the ATC mode switch when leaving the cab is MCS (Manual Control System). In this context, selecting MCS is important for ensuring that the train operates under manual control, allowing the operator to take full command of the train's movements and responses to signals.

When an engineer prepares to leave the cab, it is essential to ensure that the train is not operating under any automated systems that could create unsafe conditions. In MCS, the train's automatic features are disabled, which enhances the safety protocol when transitioning control or when exiting the cab.

This choice reflects the underlying operational safety principles where human control and decision-making are prioritized, particularly in scenarios where a train may be unattended or where automated systems might not respond accurately to situational changes.