S4
S4 trainset near Sevelen
Overview
First service	15 December 2013 (2013-12-15)
Current operator(s)	Südostbahn
Route
Termini	Sargans Rapperswil
Stops	28
Distance travelled	141.9 kilometres (88.2 mi)[1]
Average journey time	2 hours 23 minutes
Service frequency	Hourly
Line(s) used	Chur–Rorschach railway line Rorschach–St. Gallen railway line Bodensee–Toggenburg railway line Uznach–Wattwil railway line Rapperswil–Ziegelbrücke railway line
Route map Legend S5 S40 VAE to Pfäffikon SZ 59.4 Rapperswil S5 S7 S15 S40 S6 S17 S7 to Zürich HB S5 S15 to Rüti ZH Jona 46.3 34.4 Uznach S6 S17 S6 S17 to Ziegelbrücke 31.0 Kaltbrunn Ricken Tunnel S2 to Nesslau-Neu St. Johann 20.0 53.2 Wattwil S2 S9 50.7 Lichtensteig S2 S9 S9 to Wil Thur Wasserfluh Tunnel 46.4 Brunnadern-Neckertal S2 42.4 Mogelsberg S2 37.1 Degersheim S2 St. Gallen Appenzell Ausserrhoden 33.4 Schachen S2 S23 to Appenzell 29.7 Herisau S2 S23 S81 RE1 S23 to Gossau SG Appenzell Ausserrhoden St. Gallen (bridge over the Sitter) 24.4 St. Gallen Haggen S2 S81 S20 S21 S22 to Gais 21.5 80.5 St. Gallen VAE S1 S2 S5 S20 S21 S22 S81 S82 S20 S21 S22 to Trogen Rosenberg Tunnel 78.2 St. Gallen St. Fiden S1 S2 S5 S81 S1 S82 RE1 to Romanshorn 72.8 Mörschwil S2 68.0 Goldach S2 S5 66.3 Rorschach Stadt S2 S5 S7 S25 to Rorschach Hafen 65.0 Rorschach S2 S5 S7 S25 S25 rack railway to Heiden 62.8 Staad S2 S5 57.8 Rheineck S2 S5 S26 S26 rack railway to Walzenhausen 53.8 St. Margrethen S2 S5 S7 S3 R5 S7 S3 R5 to Bregenz / Dornbirn 51.1 Au SG S2 47.9 Heerbrugg S2 44.3 Rebstein-Marbach S2 41.2 Altstätten SG S2 Bus link Altstätten Stadt S24 S24 rack railway to Gais 35.3 Oberriet 30.2 Rüthi SG 24.6 Salez-Sennwald 15.9 Buchs SG S2 S2 to Feldkirch 11.0 Sevelen S17 to Ziegelbrücke 0.2 Sargans S12 S17 S12 to Chur [2][3] This diagram: view talk edit

The S4 is a railway service of the St. Gallen S-Bahn that provides hourly service between Sargans and Rapperswil via St. Gallen, connecting stations in the cantons of St. Gallen and Appenzell Ausserrhoden. The section near Lake Constance (Bodensee) is also part of the Bodensee S-Bahn.^[4] Südostbahn (SOB), a private company primarily owned by the federal government and the canton of St. Gallen, operates the service.

Between 2013–2023 it operated over a circular route (German: Ringzug), also running over the Ziegelbrücke–Sargans railway line south of the Walensee.

The S4 operates hourly between Sargans and Rapperswil via St. Gallen. The service is operated by Stadler Rail Flirt/Flirt-3 EMUs of Südostbahn (SOB).

The S4 operates with the S6, S17 and IR Voralpen-Express between Rapperswil and Uznach, combining for four trains per hour and direction. The S4 does not call at intermediate stations Blumenau and Schmerikon. The S4 and the S2 combine for half-hourly service between Wattwil and Altstätten SG. Service between St. Gallen and St. Margrethen is more frequent due to the additional S5, which runs hourly. Between Wattwil and Uznach, the S4 combines with the IR Voralpen-Express for a half-hourly service.

The service links the Alpine Rhine Valley and the city of St. Gallen with the Obersee region, via Herisau, the capital of the canton of Appenzell Ausserrhoden, and the Toggenburg Valley.

S4 Rapperswil – Uznach – Wattwil – Herisau – St. Gallen – Rorschach – St. Margrethen – Altstätten SG – Buchs SG – Sargans

• Rapperswil
• Uznach
• Kaltbrunn
• Wattwil
• Lichtensteig
• Brunnadern-Neckertal (stops only on request)
• Mogelsberg (stops only on request)
• Degersheim
• Schachen (Herisau) (stops only on request)
• Herisau
• St. Gallen Haggen
• St. Gallen
• St. Gallen St. Fiden
• Mörschwil
• Goldach
• Rorschach Stadt
• Rorschach
• Staad
• Rheineck
• St. Margrethen
• Au SG
• Heerbrugg
• Rebstein-Marbach
• Altstätten SG
• Oberriet
• Rüthi SG
• Salez-Sennwald
• Buchs SG
• Sevelen
• Sargans

Prior to the December 2013 timetable change, the S4 operated between St. Gallen and Uznach. Local service between Uznach and Sargans was handled by an hourly regional service that ran between Ziegelbrücke and Chur.^[6] Service southeast of St. Gallen toward Sargans was handled by various local services, but only the Rheintal-Express [de] operated over the whole route.^[7]

Südostbahn introduced the new S4 on 15 December 2013 as a circle line (German: Ringzug), which was sometimes referred to as the 'Alpstein round trip' (Alpsteinrundfahrt).^[8] Until 9 December 2023, the service operated hourly in both a clockwise and counter-clockwise direction. A full journey around the circle took approximately three hours. In Uznach, which lies to the west of the junction between the Uznach–Wattwil and Rapperswil–Ziegelbrücke lines, the trains reversed their direction of travel before continuing on the circle route.^[9]

With the 10 December 2023 timetable change, the circular operation ended. The S4's new termini became Rapperswil and Sargans, respectively, and the new S17 began running between Rapperswil and Sargans via Ziegelbrücke. However, the trainsets operating as S4 and S17 services continue as the respective other line from Sargans, so that passengers can still take the circular route around Alpstein without changing trains in Sargans; a change of trains is nonetheless required in either Uznach or Rapperswil.^[10] Rerouting of the S4 and introduction of the new S17 service were made possible through the expansion to dual track between Uznach and Schmerikon (constructed between 2021 and 2023) on the Rapperswil–Ziegelbrücke railway line.^[11]

• 2018 brochure