To my knowledge, the brakes on American trains work like this: You can selectively increase the braking force by gradually reducing the pressure in the system. However, you cannot gradually reduce the braking force, but only cause a full release. This is how valve systems in freight locomotives work. In the case of the F40PH-3C (in the game), I am able to freely manipulate the pressure, both ways (e.g. from 90 PSI to 100 PSI). Is it prototypical?