on the Ring line, in West Berlin trains reversed at Köllnische Heide. Only the northern track was operated between Köllnische Heide and Neukölln. In the late 1970s, the embankment on the northern side threatened to sag, causing the East German Railways to move operations on to the southern suburban track. This solution, however, only continued for a few years, as in early September 1980 both the Ring line and the short branch to Köllnische Heide were closed as a result of a strike by employees of the S-Bahn resident in West Berlin. On the East Berlin side, the line gradually closed. Initially, only the first 200 metres across the border were affected. At the end of the 1980s the last tracks were removed. Only the underpass under the main line remained. Reopening of the line after the fall of the Wall After Berliner Verkehrsbetriebe took over operation of the S-Bahn in West Berlin in 1984, initially only the rump operation on the Stadtbahn and on the Dresden line were maintained. Other lines were restored between 1984 and 1985 - Wannsee line, the North-South Tunnel and the Northern line. The reopening of the southern section of the Ring line in the western part of Berlin was scheduled to start in 1991 since the BVG took over the operation of the S-Bahn in West Berlin in 1984. This has been depended on the pressure groups and the government who decided to bring forward owing to the response from the West Berlin commuters: There was popular pressure to bring it forward in 1988 and 1989. It was agreed to reopen the Ring line between Westend and Schöneberg by 1992 and extend it to Sonnenallee in 1994, when the Berlin government is changed before the fall of the Berlin Wall. After the start of this work, the Berlin Wall fell and the Germany is reunified. This meant that it was now possible to extend the Ring line immediately to the east on the existing line. The Baumschulenweg–Neukölln link line was part of the first line to be put back into traffic. Construction began on 16 December 1990 for the section from Baumschulenweg to Köllnische Heide. The Neukölln to Treptower Park section of the Ring line followed later after the first part of the ring line is completed in 1994, because work was required at Treptower Park station. On 17 December 1993 the S-Bahn was