What is indicated by flashing green signals for approaching trains?

Flashing green signals for approaching trains specifically indicate that trains in Manual Control System (MCS) and Manual Automatic Train Control (MATC) are permitted to proceed. This signal essentially communicates that the trains can continue their journey without stopping, as there are no obstacles or other concerns that would necessitate a halt. In the context of train operations, receiving a flashing green signal is crucial for maintaining efficiency and schedule adherence while ensuring safety on the tracks.

The other options suggest scenarios that would not apply in this context. For instance, a requirement to stop or wait would be indicated by different signal types, and the indication that the track is clear for all trains is more general than what the flashing green conveys for specific system operations. Similarly, the need to slow down in preparation for a signal change pertains to other signal indications and does not align with the meaning of a flashing green signal in the systems specified.