In Release mode, what immediate action must an engineer take when an emergency brake application is triggered?

In the context of an emergency brake application, the immediate and crucial action for an engineer is to review train diagnostics. This step is essential because understanding the condition of the train and any associated systems helps the engineer assess the situation accurately. The diagnostics will provide information on why the emergency brake was triggered, which could be due to various factors including technical issues, signaling problems, or external hazards.

Taking the time to analyze the train diagnostics allows the engineer to make informed decisions on the next steps. For example, if the diagnostics indicate a system fault, the engineer needs to address that before considering moving the train or responding in any operational capacity. The diagnostics help ensure that safety is maintained throughout the response process and reduce the risk of further incidents.

Other options, while they may be relevant in later stages of the response protocol, do not prioritize the immediate safety assessment required in the aftermath of an emergency brake application. Understanding the train's current status is the first and most critical step that enables the engineer to respond appropriately to ensure the safety of both the train and passengers.