What depth of water over the ties prevents a train from passing according to safety rules?

The correct depth of water over the ties that prevents a train from passing, according to safety rules, is six inches. This depth is critical because water depth can significantly affect traction, stability, and the overall handling of the train. When the water level reaches or exceeds six inches, it poses a risk of flooding the track bed, which could lead to potential derailment or other hazards that compromise the safety of the train and its passengers.

At this depth, the train's weight combined with the buoyant forces can lead to instability, making it difficult for the train to maintain proper track alignment. Safety regulations are designed to protect both the train crews and the passengers, thus a clear threshold such as six inches provides a straightforward guideline for operational safety. It is vital for train operators to be aware of these thresholds to ensure safe operations under varying weather conditions.