What defines a segment of track within defined limits upon which trains may operate only as authorized by an employee-in-charge?

The defined limits for a segment of track where trains may operate only as authorized by an employee-in-charge are referred to as "working limits." These limits ensure that safety protocols are followed and that trains operate only under specific conditions, typically when work is being performed on the track. The establishment of working limits helps to manage any risks associated with maintenance or other activities occurring on the track, ensuring that all personnel are aware of where operations are permitted and under what circumstances.

Understanding the concept of working limits is crucial in maintaining safety and efficiency within rail operations. In contrast, other types of tracks (such as yard track and main track) serve different purposes, and controlled track pertains to areas where train movements are regulated more broadly, but not necessarily tied to the authorization of an employee-in-charge for specific operational limits.