The Aargau S-Bahn (German: S-Bahn Aargau) is an S-Bahn-style regional rail network serving the canton of Aargau, Switzerland.
Upon the timetable change on 14 December 2008, an S-Bahn numbering system was introduced for regional rail services in Aargau.
The new S-Bahn network was designed to complement the existing adjacent S-Bahn networks in Central Switzerland, Zurich and Basel. With that in mind, the line numbers selected for the new network were in the 20s (except the S14 Menziken–Aarau–Schöftland), so that there would be no conflict with the other networks.
The new network was essentially a redesignation of its existing lines. No new stops were built for it, and no new rolling stock was purchased. In some cases, however, certain services in the 2007/2008 timetable were modified (e.g. the Langenthal–Baden through connection), and to a limited extent the frequency of services was increased.
S 14: Menziken – Aarau – Schöftland (WSB)
Timetable: Mondays to Saturdays at 15-minute intervals to 21:00, then at 30-minute intervals to midnight. Sundays at 30-minute intevals to midnight.
Rolling stock: Be 4/4 + ABt or Bt, ABe 4/8, Be 4/8 (metre gauge)
Operated by Wynental- und Suhrentalbahn (trading as AAR bus+bahn)
S 23: Langenthal – Olten – Aarau – Lenzburg – Brugg – Baden
Timetable: Daily at hourly intervals to midnight; Monday to Friday mornings and evenings, additional trains between Brugg and Lenzburg.
Rolling stock: NPZ Domino, HVZ trains: Brugg–Lenzburg RABe 520 (Stadler GTW)
Operated by SBB-CFF-FFS
S 26: Aarau / Lenzburg – Wohlen – Muri – Rotkreuz
Timetable: Daily at hourly intervals between Aarau and Rotkreuz, and at hourly intervals between Lenzburg and Rotkreuz, scheduled so as to make the services between Wohlen and Rotkreuz operate at 30-minute intervals; Monday to Friday mornings and evenings, additional trains between Lenzburg and Muri.
Rolling stock: Stadler FLIRT
Operated by SBB-CFF-FFS
From 2008 to 2010, due to insufficient track capacity between Lenzburg and Hendschiken, the Aarau S26 trains ran via Lenzburg, and the intermediate trains terminated at Othmarsingen, where passengers had to change to the S3 or S23.
S 27: Baden – Waldshut / Bad Zurzach
Timetable: Daily at 30-minute intervals to midnight.
Rolling stock: NPZ
Operated by SBB-CFF-FFS
S 28: Zofingen – Lenzburg
Timetable: Daily at hourly intervals to midnight; Monday to Friday mornings and evenings at 30-minute intervals.
Rolling stock: RABe 520 (Stadler GTW)
Operated by SBB-CFF-FFS
S 29: (Langenthal – Olten –) Aarau – Wildegg – Brugg – Turgi
Timetable: Daily at hourly intervals to midnight; Mondays to Fridays, nine direct trains Langenthal–Turgi and return (at these times, services between Aarau and Turgi are at 30-minute intervals).
Rolling stock: Stadler FLIRT HVZ trains: NPZ Domino
Operated by SBB-CFF-FFS
