What should be done if there is a straight air rupture on a PA4 train?

In the scenario of a straight air rupture on a PA4 train, operating the train normally but under caution is appropriate because such a rupture does not immediately jeopardize safety. A straight air rupture indicates that there is a loss of air pressure in the brake system, which can affect the functionality of the brakes; however, it does not necessarily mean that the train must be brought to an immediate stop.

Operating under caution allows the crew to maintain control of the train while they assess the situation and make appropriate decisions to ensure safety. The crew would need to monitor the braking performance and be prepared to stop the train if any further issues arise. This approach balances operational needs with safety, as stopping the train suddenly in a potentially unstable situation could lead to other complications.

In contrast, notifying the dispatcher immediately is typically a subsequent step, but assessing the immediate impacts and maintaining control is prioritized first. Stopping at the nearest platform or reducing speed significantly may not always be necessary or safe depending on the location and situation. Therefore, the decision to operate normally under caution provides the necessary flexibility to handle the situation effectively while keeping safety paramount.