A. In this position of the brake valve, the brake pipe is connected
directly with the atmosphere through the large ports in the valve,
causing a sudden reduction of brake pipe pressure, this in turn causing
the distributing valve on the engine and all operating triple valves on
cars in the train to move to emergency position, thus insuring a quick
and full application of the brake.
91. Q. How should the brake valve be handled when making an emergency
application of the brake?
A. The valve should be placed in full emergency position and left there
until the train stops, even though the danger may have disappeared.