A mandatory directive refers to what type of information?

A mandatory directive refers specifically to critical operational information such as movement authority or speed restrictions that must be followed by train crews to ensure safety and compliance with regulations. This type of information is non-negotiable and is essential for the safe movement of trains. For example, a speed restriction is put in place to alert crews about limitations on how fast they can operate their train in certain areas, usually due to specific conditions such as track maintenance, operational issues, or safety protocols.

In contrast, the other options represent different types of information that, while important, do not possess the same level of immediacy and required compliance that characterizes mandatory directives. Weather advisories, for example, provide crucial information but do not dictate actions that must be taken by train crews in the same authoritative manner. Equipment maintenance schedules and train route planning, while essential for operational efficiency, are more about planning and management rather than urgent directives that must be followed at all times.