How far do "track and time" limits extend when designated by "switch no"?

The correct answer is that "track and time" limits extend to the signal governing movement over the switch. This is because "track and time" refers to the authority granted to a train crew to occupy a section of track, and the specific designation, such as "switch no," indicates the point at which that authority begins and ends. When defined by a switch number, the limits are set by the signals that govern the movement associated with that switch.

The signal serves as a key control point, allowing the dispatcher to manage and ensure safe train operations. The movement is typically influenced by signals, which provide vital information about track occupancy and train status. Therefore, the authority to occupy the tracks ends at the signal, ensuring that movements are conducted in a controlled and safe manner without overlapping with any other train movements.

Other considerations for the other options are that yard limits typically encompass larger areas and are not specifically tied to a single switch. Station limits would also extend further than what is defined by just a switch number. Limiting the authority to the end of a siding does not account for the signal aspect, which is the critical factor in determining the track and time limits established at a switch.