>I suuppose they would lend the cars to smaller railroads which couldn't afford their own instruction cars. In addition to training train crews, I'd guess they might also have been used to train maintenance people in the care and feeding of the equipment.
I suspect that Westinghouse also used those cars for road testing. They could insert gauges into various pipes and put the car into a train. The test crew could watch the action of the brake equipment as the train brakes were applied and released in service.
Westinghouse and New York Air Brake Co. both had large test racks of brake pipes, mounting brackets and valves lined up crossways in one building. Westinghouse at Wilmerding could simulate a 150 car train. The pipes were 50 feet long, I think, with angle cocks and air hose connections at each end, and the valves and cylinders in the center aisle.
You could charge the "train" and handle the air with any one of several different types of locomotive brake equipment. As the brakes were operated, metal flags on the brake cylinders would move in and out, and you could see the progress of the application and release.
They also had pressure gauges at various points in the train, for brake pipe, brake cylinder and reservoir pressures. I used the Westinghouse rack several times to validate computer models of train operation for accident investigations, and I found that I could get very close to reality. The Westinghouse engineers (and New York, as well, when I worked with them earlier) were true gentlemen and experts in the arcane art and science of air brakes. "Fiddling with the air" on their test rack was a blast in more ways than one.