What characterizes an "inverse" gradient in a train brake system?

An "inverse" gradient in a train brake system is characterized by having a higher brake pipe pressure at the rear of the train compared to the head end. This situation typically arises due to various factors such as a malfunction or an operational choice that leads to improper pressure distribution along the train. In a properly functioning train braking system, one would usually expect a consistent or decreasing pressure along the length of the train from the front to the rear. However, in the case of an inverse gradient, this condition can affect the performance of the brakes, potentially leading to uneven braking where the rear cars may not be effectively controlled relative to the front cars.

The other choices do not represent the characteristics of an inverse gradient; they either describe normal functional states of the braking system or conditions that would not align with the concept of an inverse gradient. For instance, equal brake pressure throughout the train signifies a well-functioning system, while being fully charged or having brakes in the release position indicates that the system is not actively applying any braking force, which contrasts with the idea of an inverse gradient where pressure dynamics are at play.