What does a track warrant authorize under TWC limits?

A track warrant is a form of authorization that allows a train or crew to occupy a specific section of main track within designated limits, referred to as Track Warrant Control (TWC) limits. This authorization is issued by a control operator and is specifically designed to provide safe guidance for train movements, ensuring that the main track is properly managed and that operational safety protocols are followed.

Under TWC limits, the primary function is to allow authorized movements only on the main track where necessary precautions are followed, thereby preventing collisions and ensuring safe operations. The track warrant specifies the limits of where the train may operate, which is crucial for maintaining control on busy rail segments.

The other options do not accurately reflect the nature of a track warrant's authority. For instance, sidings within a yard may not necessarily fall under the jurisdiction of a track warrant unless explicitly authorized. Similarly, free movement without restrictions or movement in both directions without any signals does not align with the structured and safety-focused framework that track warrants are designed to provide. Thus, the provision of main track use under a control operator as authorized by a track warrant is fundamental to maintaining safe and efficient rail operations.