What speed must be maintained during initial movement in ATC Bypass mode?

During initial movement in ATC Bypass mode, maintaining Restricted Speed is crucial for safety and control. Restricted Speed is defined as a lower speed that allows operators to navigate track conditions more cautiously, especially in situations where automatic train control systems are not active. This speed ensures that the operator has adequate time to respond to any obstacles, signals, or potential hazards on the track. In the context of ATC Bypass mode, where the automated systems are temporarily disabled, adhering to this speed limit mitigates risks and enhances safety while allowing the operator to regain full control of the train.

The other speed options—normal, high, and medium—are not appropriate for the initial phase in ATC Bypass mode as they do not provide the necessary caution that Restricted Speed offers. Normal speed could be too fast given the loss of automated assistance, while high speed poses an increased risk of incidents or accidents. Medium speed, although slower than normal speed, may still not be slow enough to ensure proper operational safety during this critical period. Thus, Restricted Speed is the correct choice to prioritize safety in this operational context.