After a train that has stopped for a non-passenger reason, when can it resume speed?

The correct choice is based on the operational procedures outlined by NORAC concerning train movements after a stop for non-passenger reasons. A train that has stopped for such reasons is typically required to resume speed only after it has passed a signal displaying a proceed indication. This protocol is in place to ensure that the train is entering a safe and clear section of track before it accelerates, minimizing the risk of accidents and confirming that it is safe to proceed.

Passing a signal displaying a proceed indication indicates that the track ahead is clear and that it is safe for the train to continue its journey. This aspect of signaling is critical to maintaining safety standards on the rail network, allowing operators to make informed decisions based on the current track conditions.

The other choices, while relevant to various scenarios in train operations, do not specifically encompass the necessary safety checks that must be adhered to after a train has stopped for non-passenger reasons. For example, relying solely on a crew member's signal or dispatcher permission does not take into account the established signaling system that is designed to provide an objective measure of safety for train movements. Similarly, continuing to the next block without confirming a proceed signal could lead to unsafe conditions if that block is not clear.