What should be ensured of the rear car brake pipe pressure before descending a mountain grade?

Ensuring that the rear car brake pipe pressure is within a specific range of the regulating valve setting before descending a mountain grade is crucial for effective brake operation and overall safety. This range is determined by the brake system design and provides a standard for maintaining adequate braking force throughout the descent.

If the pressure is maintained within this specified range, it helps to ensure that the brakes will engage effectively when needed, allowing for safe control of the train's speed. This is particularly important when managing potential dynamic forces while descending a grade, as improper pressure levels could lead to inadequate braking response or excessive brake wear.

The correct pressure range facilitates proper operation of the train's braking system, offering the necessary safety measures against overheating brakes and maintaining optimal performance during the descent.