In what situation can hand brakes on moving cars be operated?

The operation of hand brakes on moving cars is specifically designed for emergency situations. This ensures the safety of train operations, as engaging hand brakes while a train is in motion can lead to unpredictable and hazardous outcomes if not conducted under appropriate circumstances. In emergencies, such as when a train is moving uncontrollably or when an immediate stop is necessary, safely applying the hand brakes can help slow down or halt the train, thus preventing accidents.

The other scenarios, while they may seem plausible, do not align with safe operating procedures. Engaging hand brakes during standard operations could compromise the stability and control of the train, and training new crew members should primarily focus on safe practices rather than potentially dangerous situations. Similarly, low visibility is not a valid reason to operate hand brakes on moving cars, as it introduces risks related to visibility and awareness that do not justify such actions during those conditions. Hence, operating hand brakes on moving cars is constrained to emergency instances to maintain safety and control.