How long are TGBO and track bulletins valid for the train or engine crew?

The validity of TGBO (Track General Bulletin Order) and track bulletins for train or engine crews is fundamentally tied to the operational procedures and safety protocols of railroad operations. When the answer states that they are valid for the entire tour of duty unless canceled or expired, it emphasizes the importance of maintaining up-to-date and relevant information throughout the duration of the crew's work period.

This means that once a TGBO or track bulletin is issued, it remains applicable for all relevant operations and conditions that the crew may encounter until it is expressly canceled or reaches its specified expiration. This practice is essential for ensuring that train and engine crews remain aware of any changes in track conditions, signals, or operational instructions that could affect their duties and safety during their entire shift. The provision for cancellation or expiration ensures that only the most current and relevant information is utilized, avoiding confusion or miscommunication that could arise from using outdated bulletins.

In contrast, other responses suggest validity limited to specific circumstances or shorter durations, which may not adequately provide the necessary information for safe train operations over a crew's complete working period.