Air Brake System: Shutoff Valves on Trailers

What is the proper position of shutoff valves on different trailers in a combination vehicle?

Should the shutoff valves on the rear of the last trailer be open or closed? On the first trailer and a set of doubles? On the middle trailer of a set of triples?

Final answer:

Generally, the shutoff valves on the rear of the last trailer, the first trailer and a set of doubles should be open, while the valve on the middle trailer of a set of triples should be closed for optimal functionality of the vehicle's air brake system.

Explanation:

The setting of the shutoff valves depends on the specific needs and circumstances of the situation. However, speaking in general terms, the shutoff valves on the rear of the last trailer should be open to allow air flow for the brake system. Likewise, the valves on the first trailer and a set of doubles should be open as well. The valves on the middle trailer of a set of triples should be closed because it is being supplied air from both ends. This increases efficiency and safety of air brake system operation in triple combination vehicle.