Route of S4
0.0 Unna 1.1 Unna West 3.9 Unna-Königsborn 7.2 Massen 8.7 Dortmund-Wickede 10.2 Dortmund-Wickede West 11.8 Dortmund-Asseln Mitte 14.2 Dortmund-Brackel 15.1 Dortmund Knappschaftskrankenhaus 16.8 Dortmund-Körne 17.8 Dortmund-Körne West 20.1 Dortmund Stadthaus 21.3 Dortmund Möllerbrücke 22.3 Dortmund West 23.1 Dortmund-Dorstfeld S1S2 25.9 Dortmund-Marten Süd 27.9 Dortmund-Germania 28.8 Dortmund-Somborn 30.3 Dortmund-Lütgendortmund
Source: German railway atlas[1]

Line S 4 is an S-Bahn of the Rhine-Ruhr S-Bahn, running from Unna to the Dortmund suburb of Dortmund-Lütgendortmund. It is operated by DB Regio on behalf of Verkehrsverbund Rhein-Ruhr. It is operated at 30-minute intervals (15-minute intervals in the peak between Dortmund-Lütgendortmund and Unna-Königsborn) using class 422 four-car electrical multiple units.^[2]

Line S 4 runs over several lines:

• from Dortmund-Lütgendortmund to Dortmund-Germania over the new S-Bahn line (2213), opened by Deutsche Bahn on 2 May 1993,^[3]
• from Dortmund-Germania to Dortmund Stadthaus over the Rhenish Ruhr line, opened by the Rhenish Railway Company on 19 November 1874,^[4][5]
• from Dortmund Stadthaus to Unna-Königsborn over the Welver–Sterkrade line opened by the Royal Westphalian Railway Company on 15 May 1876,^[6]
• from Unna-Königsborn to Unna over the Fröndenberg–Kamen line opened by the Prussian state railways between 2 January 1899 and 1 November 1900.^[7]

S-Bahn services commenced between old Lütgendortmund station and Unna station on 3 June 1984. The section from Germania to old Lütgendortmund station was closed on 31 August 1987 and operations on the new line to Lütgendortmund commenced on 23 May 1993.^[2]

Extension of the S 4 line from its current western end in the tunnel at Dortmund-Lütgendortmund was formerly planned to be implemented with a target of opening it in 2015. This would have included an extension of the single-track tunnel to the immediate south of Dortmund-Bövinghausen station. The S 4 would run from there to Herne on the Duisburg-Ruhrort–Dortmund railway (the Emscher Valley Railway of the Cologne-Minden Railway Company) and there take over the Herne–Essen branch of the current S 2 line. The Emschertal-Bahn (RB 43) Regionalbahn service would only operate between Herne and Dorsten. The eastern section of the Emscher Valley Railway between Dortmund-Bövinghausen and Dortmund Hauptbahnhof would be used by a new line of the Dortmund Stadtbahn. For a long time funds have been available for the construction of the line to Bövinghausen, however, the financing for the operation of the line is not guaranteed. The Emschertal-Bahn runs between Dortmund-Bövinghausen and Herne every hour, but the S2 would run between Herne and Essen every twenty minute as an S-Bahn service, so the Verkehrsverbund Rhein-Ruhr would have to fund the increased services through savings in other areas. Upon taking office, the transport minister Oliver Wittke called for all such proposals to be re-evaluated. The line extension has been removed from the integrated transportation plan for North Rhine-Westphalia; a resubmission is possible from 2015.

References

Unna-Königsborn station