What does a lit brake release light signify to the engineer?

A lit brake release light signifies that all air brakes are released. This is crucial for the engineer as it indicates that the train is in a state where it can move freely without any brake pressure applied to the wheels. Understanding that the air brakes are released is essential before the train can be safely moved.

When this light is illuminated, it assures the engineer that the braking system is functioning properly and that the train is ready to proceed without any risk of unintended braking, which can cause delays or unsafe conditions during operations.

While it may seem tempting to think that the other options also pertain to train readiness, they do not reflect the specific and critical information that the lit brake release light provides. Knowing that all air brakes are released is vital for proper train operation and safety.