S-Bahn Station Sihlpost Zurich / Tracks 51–54

As a temporary measure, a provisional facility with four additional tracks (tracks 51–54) was built south of track 3 to relieve the main hall (tracks 3–18) of S-Bahn traffic. It is offset from the main tracks and was to be dismantled by 2013 with the construction of the underground Löwenstrasse station. On the side of Sihlpost passenger station, the post railway station of the Sihlpost sorting center adjoined it.

Tracks 51 to 54 are referred to as Sihlpost station, which can be described as a provisional station but has established itself as an important part of S-Bahn operations at Zurich's main railway station. The track numbering was deliberately chosen to deviate significantly from the existing numbering to make it clearer to passengers that this is a separate station section.
Source: Wikipedia