The tunnel begins directly after the Hauptbahnhof where its two tracks branch off the Hamburg-Altona link line and immediately dive under it.

Shortly north of the station, the railway climbs at a maximum gradient of 4.0% to reach ground level.

During the planning and construction of the large housing estate of Osdorfer Born in north-western Hamburg, consideration was given to increasing S-Bahn services on the Hamburg-Altona link line (Verbindungsbahn), which at that time had services running at a minimum interval of 150 seconds.

The signalling system allowed trains to run 90 seconds apart but the slightest deviation from the timetable would have created a major difficulty.

Subsequently the rest of the station building was demolished because the risk of its collapse due to the driving of the tunnel under it was considered to be unacceptable.

During the construction of the tunnel it was decided to extend the S-Bahn to Harburg, requiring increased capacity at the Hauptbahnhof.

Following the example of Munich's Trunk line 2, a second city tunnel is planned for Hamburg;[2] linking the Hauptbahnhof with a new station in Altona-Nord at a cost of €3 billion.