If the On-board PTC apparatus fails en route, what must the engineer do first?

The correct response emphasizes the importance of communication in the event of an onboard PTC (Positive Train Control) apparatus failure. When such a failure occurs, the engineer must first notify the Conductor or Dispatcher to ensure that proper protocols are followed and that all operational safety measures are maintained. This communication is essential for assessing the situation more effectively and determining any necessary actions to be taken in response to the failure.

Informing the Conductor or Dispatcher allows for the coordination with other train operations, which may include rerouting trains, adjusting schedules, or implementing other safety measures to prevent accidents or delays. This step is critical because it establishes a clear line of communication that is vital for managing the safety and efficiency of rail operations during any failure.

While assessing the situation and proceeding with caution may seem like logical immediate actions, they are not sufficient without first informing the relevant personnel. Likewise, removing the failed apparatus is not practical while the train is still in operation and may not be possible depending on the nature of the failure. Therefore, notifying the Conductor or Dispatcher acts as a first-response measure that enables all subsequent actions to be taken effectively and safely.