Which condition allows for cutting out air brakes on multiple cars?

Cutting out air brakes on multiple cars is allowed when the air brake devices can be safely isolated. This means that, under certain circumstances, it is possible to disable the brakes on specific cars without compromising the overall safety of the train. This situation arises when it has been determined that the brakes on those cars are not functioning correctly or cannot be reliably used while ensuring that the train can still operate safely.

Maintaining safety and operational integrity is paramount in train handling, so any actions taken to isolate brakes must adhere to established protocols and safety guidelines. In practice, this allows for necessary repairs or adjustments to be made while minimizing disruption to the entire train system.

In scenarios like budget cuts or routine inspections, actions regarding the air brakes would not be governed by the need to isolate them purposefully. Mechanical issues may prompt a closer investigation into whether isolation is necessary, but the key consideration is ensuring that the air brake devices can indeed be safely isolated. Thus, the correct choice reflects the importance of safety in the operation and maintenance of train air brake systems.