Can air brakes be relied upon to hold a train when it is left unattended?

Air brakes are an important component in train operations, primarily used for stopping and controlling trains while in motion. However, they cannot be relied upon to hold a train unattended due to several factors that can affect their performance.

One key issue is that air brakes require a constant supply of air pressure to function effectively. If a train is left unattended, the loss of air pressure could lead to a failure in braking force, allowing the train to move unexpectedly. Additionally, environmental factors such as temperature changes can affect the air pressure in the brake system.

Moreover, mechanical or maintenance conditions can lead to brake system failures if they are not regularly checked. This means that even if the air brakes are set when the train is left unattended, there is no guarantee that they will remain effective, which poses a safety risk, especially on slopes or gradients.

In contrast to the other responses, the assertion that air brakes cannot be depended on when the train is unattended aligns with best practices in railroad safety, which typically require additional measures such as setting hand brakes or using wheel chocks to ensure a train remains secure when not in operation. These practices highlight the importance of a comprehensive approach to train safety rather than relying solely on air brakes.