When should the automatic brake valve be cut out?

The correct answer focuses on the specific procedure involving the automatic brake valve during brake pipe leakage tests. Cutting out the automatic brake valve means that it is temporarily removed from the circuit, allowing for a direct connection to the brake pipe without interference from the valve’s operations. This is necessary for accurate testing, as it ensures that the test results reflect the actual state of the brake pipe without any influence from the automatic brake system.

In this context, ensuring that there are no leaks in the brake pipe is crucial for the safety and reliability of train operations. By isolating the automatic brake valve, personnel can properly assess whether the brake pipe system is holding pressure as required.

The other scenarios—such as regular operations, emergency situations, and stopping at signals—do not require the automatic brake valve to be cut out. In these situations, it is essential for the automatic brake system to function correctly, allowing for proper braking performance and control of the train.