Most of the content around the 1960's BR region which use an enhanced version of the Westinghouse Air Brake system automatically apply the brakes when disconnected from the train, regardless of the incline. (Air pressure, mostly supplied by the locomotive/s, is used to keep the brakes OFF. When the air pressure releases, the brakes apply. Thus, if a consist accidentally disconnects from the train via something like coupler breakage, the consist stops on its own).
You are using USA themed rollingstock, correct?