How is movement authorized on a main track in Form D Control System (DCS) territory?

Movement on a main track in Form D Control System (DCS) territory is authorized by Form D line 2 because it explicitly provides the necessary instructions and conditions under which a train may move. Form D is an essential component that communicates critical information regarding train movements, such as any restrictions or limits placed on the movement, which must be understood by the crew for safe operations.

In DCS territory, the structured and formal nature of the Form D ensures that all personnel involved in train operations are aware of their authority and the specific conditions that apply, helping to maintain safety and coordination on the main track. The use of Form D line 2 is particularly crucial as it relates specifically to the authorization of movements, distinguishing it from other forms of communication or tools that might not convey the required levels of detail and authority needed for such actions.

Routes determined solely by verbal commands, automated signals, or crew discretion lack the formalized approach necessary for safe operation in DCS territory, which relies on precise and documented methods of authorizing train movements.