Under what circumstance must air brakes be cut out?

The requirement to cut out air brakes is primarily related to the functionality and safety of the train operations. When a brake does not release properly, it can create significant safety hazards, including preventing a car from moving when needed, which can lead to accidents or further mechanical issues. Additionally, if a car must be moved that has an overheated bearing, it is critical to cut out the air brakes to minimize the potential risks associated with a failing brake system while also ensuring the overheated component does not exacerbate the situation.

This decision prioritizes safety by allowing for the movement of the equipment without the risk of compromised braking. In operations, a car with malfunctioning brakes or mechanical issues needs to be handled differently to prevent accidents, and cutting out the brakes in this context mitigates those risks.