S4 (Rhine-Ruhr S-Bahn)
Introduction '''Line S 4''' is an S-Bahn of the Rhine-Ruhr S-Bahn, running from  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 ) using class 422 four-car electrical multiple units.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,* from Dortmund-Germania to Dortmund Stadthaus over the Rhenish Ruhr line, opened by the Rhenish Railway Company on 19 November 1874,* from Dortmund Stadthaus to Unna-Königsborn over the Welver–Sterkrade line opened by the Royal Westphalian Railway Company on 15 May 1876,* from Unna-Königsborn to Unna over the Fröndenberg–Kamen line opened by the Prussian state railways between 2 January 1899 and 1 November 1900.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.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