If the PTC apparatus displays an incorrect speed, which speed will be prioritized?

The prioritization of the lower (most restrictive) speed in the event that the PTC apparatus displays an incorrect speed is critical for ensuring safety in train operations. The purpose of speed regulation systems like PTC (Positive Train Control) is fundamentally rooted in accident prevention. In scenarios where there is a discrepancy or malfunction in speed readings, opting for the most restrictive speed minimizes the risk of accidents, particularly those related to derailments or collisions.

By prioritizing the lower speed, the system ensures that even if the displayed speed is incorrect, operations remain within a safe threshold. This cautious approach aligns with the principle of erring on the side of safety, where it is better to operate at lower speeds until the issue is rectified or confirmed, rather than relying on potentially erroneous data that could lead to hazardous conditions.

Other options, such as relying on average speeds from past travels, the engineer's indicated speed, or the maximum allowable speed, do not provide the same level of safety assurance in the context of incorrect speed readings. These alternatives could lead to unsafe operational decisions that compromise train safety and integrity on the tracks.