At Zürich HB, trains of the S15 service usually depart from underground tracks (Gleis) 41–44 (Museumstrasse station).

The line runs from Niederweningen (abbreviated as "N'weningen" on the destination sign), in the north-west of the canton of Zürich, to Zurich Oerlikon and Zurich Hauptbahnhof before continuing via Zürich Stadelhofen and Uster to Rapperswil-Jona (Canton of St. Gallen).

Some services are run by Re 450 class locomotives pushing or pulling double-deck passenger carriages.

The service was started between Rapperswil and Birmensdorf on 10 December 2006, following line improvements.

With the introduction of the new timetable in late 2015, the western terminus of the service was switched from Affoltern am Albis to Niederweningen.