What essential measurement is referred to as Measurement B in the context provided?

In the context of railway maintenance and safety, Measurement B is specifically identified as the guard face gauge. This measurement is crucial because it ensures that the spacing between the guard rails and the running rail is adequate. The guard rail serves to prevent derailments and maintain safe train operations, making it vital to consistently monitor its alignment and proximity to the main rail.

This measurement helps maintain the safety and performance criteria required for railway operations, ensuring that trains can operate smoothly without risking derailment. The guard face gauge assessment is part of regular inspections and evaluations of track integrity, influencing overall safety standards within the rail system.