English: The Third Line, Belfast
Adelaide goods yard J3271 : Adelaide goods yard, Belfast (and much of the commercial area west of Adelaide station) is built on the site of the old GNR(I) workshops and locomotive depot. There was a third line between the depot and Great Victoria Street passenger station J3373 : Gt Victoria Street station, Belfast (2) and the old Grosvenor Road goods yard. Its purpose was to allow movement of locomotives and rolling stock without conflicting with passenger trains on the two running lines.

After the closure of the workshops and depot it saw little use save for a daily movement of a train of parcels vans from the new yard to Gt Victoria Street. The line had its swansong on the last day of passenger services from Gt Victoria Street, during connection of the about to be re-opened Central line to Botanic, Central and the Bangor line. A special timetable allowed Gt Victoria Street to remain open by using the third line for passenger trains which then ran via the line, through Adelaide yard before re-joining the running lines north of Balmoral.

The 11.40 “Enterprise” to Dublin is running along the Third Line having just passed under the Donegall (incorrectly shown as “Donegal” on the Google map) Road bridge. It would enter Adelaide yard along the course of the line, ending at the buffer stops, seen in J3272 : Railway at Adelaide, Belfast.