Which position of the brake valve indicates that it is not in use?

The position of the brake valve that indicates it is not in use is the handle-off position. When the brake valve is set to handle-off, it means that the braking system is disengaged, and no braking action is being applied to the train. This position ensures that the train can move freely without any unintended braking force being applied, which is essential for normal operation and safety.

In contrast, the other positions such as running release, emergency, and lap indicate active states of the braking system. Running release allows for some braking control while still enabling movement, the emergency position is used to apply maximum braking force, and the lap position is typically used to maintain brake pressure without releasing it entirely. Understanding these different positions is crucial for train operators to manage the braking system effectively and safely.