What should be done after opening or closing an angle/cutout cock?

After opening or closing an angle/cutout cock, it is essential to perform a running brake test. This procedure is crucial because it allows the operator to verify that the brake system is functioning correctly after any change has been made to the air brake equipment. The running brake test checks for proper brake application and release, ensuring that the brakes respond accurately to the controls.

This step is necessary to ensure the safety of the train and its operations, as any malfunction or error in the braking system could lead to potential accidents. By performing this test, the crew can confirm that the angle/cutout cock has been correctly operated and that the brake lines are sealed appropriately, allowing for safe operations on the track.

The other options, while relevant to different aspects of train operations, do not specifically address the immediate need to verify braking functionality after the adjustment of an angle/cutout cock. Therefore, conducting a running brake test is the appropriate action to take in this situation.