Under what condition is it permissible to run trains on flooded tracks?

Running trains on flooded tracks is a critical safety issue, and it is permissible under specific conditions to minimize the risks associated with water on the tracks. The correct condition indicates that trains may operate when the water level is below the ball of the running rail. This is significant because the ball of the rail, or the ballast that supports the rail, is designed to provide stability and support for the train. If water exceeds this level, it could lead to track instability, reduced traction, and increased risk of derailment.

Maintaining safe operating conditions is paramount, so this guideline helps operators ensure that trains can traverse the area without jeopardizing safety. The other options do not provide adequate safety measures, as running on completely dry tracks, obtaining vague authorizations without considering water levels, or relying on the temporary nature of the flood do not adequately address the potential hazards that water poses to rail operations. Therefore, ensuring that the water remains below the critical level established helps protect both the integrity of the track and the safety of the passengers and crew.