What measures should be taken if a train is to be temporarily left on the main track?

Setting appropriate hand brakes on the detached portion of the train is crucial because it ensures the safety and security of the train while it is temporarily left on the main track. Without proper braking measures, there is a risk that the train could roll or shift due to grade or other external forces. This action minimizes the chance of accidents and maintains control over the train's position. Hand brakes act as a secondary line of defense against unintended movement, which is particularly important when the train is stationary and left unattended.

Other measures, while important for different contexts, do not address the immediate risk associated with leaving a train on the main track. For example, securing cargo is essential for safety during transit but does not directly impact the train's stability while it is stationary. Ensuring the rear section is on a siding is relevant for train configuration but does not apply if the entire train is left on the main track. Notifying local authorities may be part of standard operating procedures in some situations, but it does not provide the immediate physical safety necessary to prevent movement of the train. Thus, setting hand brakes effectively prioritizes safety and control of the train's position on the main track.