If two consecutive detectors send a failure message, what must be the train's next action?

When two consecutive detectors transmit a failure message, it indicates a potential issue with the train, such as problems with the brakes or other critical components. This situation necessitates that the train must prioritize safety and ensure that any potential hazards are addressed promptly.

Stopping the train to perform a roll-by inspection allows the crew to visually assess the condition of the train and its components in a safe manner. This inspection helps identify any immediate issues that could lead to more significant problems, ultimately allowing for informed decisions on whether the train can continue its journey safely or if further action is necessary.

Continuing to operate with caution or proceeding to the next station could exacerbate any existing issues and pose risks to the safety of the train and crew, while calling the dispatcher for an update, although part of standard protocol, would not address the immediate need to inspect the train for any critical failures. Thus, the action of stopping for a roll-by inspection is the most responsible and safety-oriented decision in this scenario.