Where does authority extend from if station names are designated as the first name point?

The authority extends from the station name if there is no siding present because this indicates that the station itself serves as a critical reference point for operational control and train movements. In cases where a siding is not available, the station name becomes the definitive start of authority for that segment of the train's route. This is significant in managing the flow of rail traffic and ensuring communication about the location of trains, as it sets clear expectations for movement authority based on established stations rather than relying on additional factors that may complicate the routing or scheduling.

The other choices suggest different origins of authority, but they do not account for the scenario being addressed—specifically where a siding is not present, rendering any direct connection to neighboring stations or recent stops irrelevant in determining authority.