What criteria are met for a track to be designated as single track?

A track is designated as single track primarily when it operates under mixed block signal (MBS) territory. This classification implies that only one train can occupy a particular segment of the track at any given time, thereby facilitating safe travel for trains in a designated area. MBS territory is essential for managing train movements where two or more trains may encounter each other on sections where there is only one track available for use, thus necessitating a system of control and coordination to ensure safety.

Designations related to multiple lines for trains indicate a multi-track setup, which is contrary to the concept of single-track operation. Additionally, the exclusive use of the track for freight transport does not inherently determine it as single track, since passenger services can also operate on single-track lines. Lastly, allowing uncontrolled train movements would conflict with the very definition of a single track where there is a need for careful scheduling and control to ensure safe operations.