When should handbrakes be set on a train?

The correct answer is setting handbrakes when the third rail power will be off for 30 minutes or more. This practice is essential for ensuring safety and stability in train operations. When power is off for an extended period, there is a risk that the train could begin to roll due to gravity, especially if it is on a slope. By setting the handbrakes, the train operator ensures that the train remains securely in place until power is restored and operations can continue safely. This is a critical safety measure to prevent unintended movement of the train and potential accidents.

Other scenarios, while they may involve the use of handbrakes, do not specifically warrant their setting in the same manner as the situation described. For example, while it is good practice to set handbrakes before coupling cars together or after using dynamic braking to secure a train, these situations do not carry the same level of urgency regarding safety as the potential for rolling when power is off for a longer duration. Understanding the context and requirements of train operations helps operators effectively manage safety protocols.