What should not be placed on the same track to ensure visibility of blue signals?

To ensure the visibility of blue signals, it's essential to maintain a clear line of sight along the track. Blue signals indicate that work is underway, and they serve as a warning to anyone approaching that the track is occupied. Placing blocks on the same track can obstruct the view of these signals since blocks are large physical structures that could hide the signals from view. Keeping the track clear of any large obstructions like blocks is crucial for safety, preventing any potential accidents from occurring due to a failure to see the blue signal.

Additionally, switches, derails, and signals typically do not obstruct the visibility of blue signals in the same way blocks do. Switches are positioned strategically to allow trains to change tracks without hiding signals from view. Derails are designed to prevent unauthorized access to tracks and are generally located in a manner that maintains visibility. Signals are essential components of railway operations and are also positioned to be visible and not obstructed. Therefore, the correct approach is to avoid placing blocks in the vicinity of blue signals to ensure they remain visible to train crews.