What are examples of mandatory directives?

Mandatory directives are specific instructions or commands that must be followed by railroad personnel to ensure safe and efficient operations. Track warrants and track bulletins fall under this category because they provide essential information about track conditions, movement authorities, and operational instructions that are crucial for maintaining safety and avoiding accidents. Personnel must comply with these directives to adhere to the rules and regulations governing railroad operations.

In contrast, the other options do not constitute mandatory directives. Casual reminders are often informal and may not carry any requirement for compliance. Informal communication lacks the authority and specificity of mandatory directives, as it can often be vague or suggestive rather than prescriptive. Meetings and briefings, while valuable for information sharing and discussions, do not typically create mandatory requirements unless they result in formal directives. Therefore, track warrants and track bulletins are the definitive examples of mandatory directives in the context of railroad operations.