During what situation would a train engineer typically issue an "emergency stop"?

An "emergency stop" is typically issued by a train engineer in response to unexpected hazards. This situation arises when there is a sudden and immediate danger that requires immediate action to protect the train, its crew, and its passengers. Examples of such hazards include an obstruction on the tracks, a signal indicating danger, or any unforeseen circumstance that poses a threat to safety. In these cases, the engineer must act swiftly to halt the train to prevent accidents or collisions.

In contrast, the other situations listed do not warrant an emergency stop. Beginning a journey, making scheduled stops, and conducting regular maintenance checks are planned activities where the normal operational protocols are followed without the urgency or need for an abrupt halt due to unexpected dangers.