Which of the following is required for trains operating in ABS or DCS territory?

In ABS (Automatic Block Signal) or DCS (Direct Control System) territory, issuing authority through Form D lines 2 and 3 is essential for ensuring safe train operations. Form D provides specific instructions or permissions that allow a train to operate in a secured manner, guiding them through segments of track while ensuring compliance with safety protocols.

This requirement is crucial because it supports the controlled management of train movements, reducing the risk of collisions and ensuring that each train has the necessary authorization to occupy track segments. By issuing these forms, dispatchers can communicate vital information regarding speed, track conditions, and other operational commands to the train crew, enabling them to maintain safe distances and follow set procedures.

Other options do not align with the operational requirements of ABS or DCS territories. For example, operational guidelines necessitate that trains can operate under a framework of authority, rather than being restricted to following other trains or operating entirely independently without the structured protocols provided by the Form D documentation.