What happens when the MATC mode selection takes place while in motion?

When the MATC (Multi-Aspect Train Control) mode selection occurs while a train is in motion, the correct outcome is that the train is stopped with an emergency brake application. This safety mechanism is designed to prevent potential accidents that could arise from unintended or abrupt changes in control modes while the train is moving. The emergency brake activation ensures that the train comes to a halt safely, allowing for a controlled recovery from such situations. This protocol is essential for maintaining operational safety and ensuring that the train does not operate under a mode that could lead to unsafe conditions or loss of control.

The other options suggest alternative actions that do not align with established safety protocols in rail operations. For instance, continuing at the same speed would not address the potential for confusion or mismanagement of train control, and rapidly accelerating or switching to manual operation could put passengers and crew at risk. Thus, activating the emergency brakes is the proper safety response to such a scenario.