What should an engineer do upon noticing loss of brake pipe pressure at the rear of a train?

Upon noticing a loss of brake pipe pressure at the rear of a train, the engineer should stop and secure the train. This response is critical because a loss of brake pipe pressure indicates a potential air leak or malfunction in the braking system, which undermines the train's ability to stop safely and efficiently. Securing the train ensures that it remains in a stable position and mitigates the risk of rolling or accidents.

Continuing to monitor the situation may delay necessary actions that should be taken to address the brake pressure loss, potentially compromising safety. Increasing speed to regain pressure is not a viable solution because doing so could lead to a loss of control and prevent the train from being stopped effectively if needed. Reporting to the main office would be appropriate after ensuring the train's safety, but immediate action to secure the train is essential first. Thus, stopping and securing the train is the correct and safest course of action.