When should hand brakes be set up on a train?

The practice of setting hand brakes on a train is a crucial safety measure that is typically implemented when the train is stationary and may require additional security against unintended movement. The correct answer focuses on the scenario in which the third rail—a method of providing power to trains—is off for an extended period. When the third rail is not operational, trains may lose power, leading to a greater risk of rolling movement if not secured properly. By setting hand brakes in this situation, operators ensure the train remains safely in position until power is restored or until further action is taken.

In contrast, setting hand brakes during inclement weather is more of a precaution, as the weather alone doesn't dictate the need for brakes. Setting them when passengers disembark is also important for passenger safety, but the focus should be on keeping the train stationary during times of potential movement risk, such as when power from the third rail is absent. Finally, setting hand brakes while the train is in motion is not practical or safe, as it poses significant risks to both the train and its passengers.