What method can DCS rules use to substitute ABS rules?

In the context of DCS (Dispatcher Control System) rules, it is crucial to understand that they can employ specific methods to substitute for ABS (Automatic Block Signal) rules. The correct answer indicates that both bulletin orders and Form D line 6 can serve this purpose.

Bulletin orders are official documents that provide instructions related to the operation of trains, including temporary changes in rules or procedures. These are critical in ensuring safety and operational efficiency when standard procedures under ABS rules are modified or not applicable.

Form D line 6 specifically pertains to track authority that outlines the conditions under which certain movements can occur while bypassing the typical constraints set by ABS rules. It provides a structured approach for train movements that ensures safety and compliance, even when the ABS system cannot be used effectively.

This combination of tools—bulletin orders for situational instructions and Form D for specific authority—facilitates the management of train movements under various circumstances, ensuring that operational flexibility does not compromise safety. Thus, both methods are valid and essential for substituting ABS rules as needed.