What denotes a successful air brake test outcome?

A successful air brake test outcome is indicated by the brakes applying and releasing as demonstrated by changes in air pressure. This means that when the brakes are activated, there should be a noticeable drop in air pressure within the system, reflecting that the air is being used to engage the brakes. When the brakes are released, the pressure should return to its original level, showing that the system is functioning correctly and that the brakes are capable of both applying and releasing as needed.

This indicates the system is sealed and responsive, which is essential for safe operation. Proper functioning of the air brake system is crucial in ensuring that trains can stop effectively and safely under various conditions.

In contrast, when brakes do not apply, there is a failure in the system, which could lead to safety issues during operation. A lack of change in pressure suggests that the system is not functioning correctly, as there should always be a fluctuation when the brakes are engaged or released. Indicators showing zero pressure would imply a complete lack of pressure in the system, which is also indicative of a malfunction. Thus, the correct response emphasizes the necessity of observing functional pressure changes during testing.