An S-Bahn line, along the eastern section of the Berlin outer rail ring (Berliner Aussenring, BAR), has been planned since the 1960’s. This section of the BAR is within the built-up area – the rest was built to avoid West Berlin, and runs in a wide circle outside the city. The planned line is a north-south tangent, entirely within the former East Berlin. In the last years of the DDR, construction had already begun.
The planned Nahverkehrstangente was never abandoned, and is currently under study, but there is no prospect of construction. Even under the changed circumstances, it would still make sense. The planned DRR line began at Schönefeld airport, the current version would start at its replacement, the new Berlin Brandenburg Airport. The new airport will replace all existing Berlin airports, and will handle far more traffic then ever planned for Schönefeld. Since reunification, new housing has been built at the north-eastern edge of Berlin, close to the planned line. The northern terminus, Oranienburg, is a transfer station, and would be more important after re-opening of the 19-km Nordbahn alignment through Berlin. (Since 1952, trains to the north run via Pankow and the BAR).
The project currently ‘under consideration’ is essentially a regional service along the BAR. That limits the planned frequency to 30 minutes, and any use of S-Bahn tracks would require double-system rolling stock. (See the discussion at Bahninfo-Forum). The version proposed here is a fully separated S-Bahn line, using S-Bahn type stock (third rail), but the alignment is essentially the same. The only original elements here, are proposed new alignments through Karow and Biesdorf, and possibly via Köpenick. The tangent line would also allow interchange at the airport, with the proposed new line from Potsdam to the airport, and the proposed high-speed rail line from there to Frankfurt (Oder).
The northern terminus of the tangent line is Oranienburg (population 42 000). There are separate S-Bahn tracks alongside the BAR, as far as the Karower Kreuz, the junction with the Szczecin line. However, some sections are single-track only, including the approach to Oranienburg station, and there is no through service Oranienburg – Karow. (The present S8 ends at Hohen Neuendorf). A shorter S-Bahn alignment is possible, by adding S-Bahn tracks to the existing north-to-east curve, south of Birkenwerder.
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New stations were planned at Arkenberge (approximately at Arkenberger Damm), Schönerlinder Strasse, and Bucher Strasse.
At the Karower Kreuz, the separate S-Bahn tracks end. (Line S8 turns toward Berlin here, using the route of line S2). Ground has already been cleared (visible on this image), for extension of the S-Bahn tracks, alongside the BAR to Wartenberg. However, the S-Bahn tracks must cross the BAR, from the Berlin side to the ‘outer’ side, and they must cross the Szczecin line itself, and the junction tracks.
The official plan is a two-level station (Turmbahnhof) in the middle of the junction, which (by definition) is inconveniently located. An alternative is to re-route the S-Bahn through the existing Karow station. That requires a new link across the A114 motorway to the alignment of the Heidekrautbahn. In fact, this is not the original Heidekrautbahn, but a link line built in 1950. It would be double-tracked: it already has a grade-separated junction into Karow station. Instead of the planned stations Bucher Strasse and Schönerlinder Strasse, there would be a station at Lindenhof. In Karow station, the new S-Bahn would simply share the existing platforms with the S2.
South of the station, a new S-Bahn curve would be built alongside the existing north-to-east curve, to rejoin the officially planned alignment, with possible stations at Karower Damm and at Malchow.
About 4 km further is Wartenberg station, terminus of S-Bahn line S75. The planned S-Bahn tracks simply connect to the existing island platform at Wartenberg. From here to the Biesdorfer Kreuz, there are again separate S-Bahn tracks (about 7 km). An additional station was planned at Burknersfelde, approximately at the Landsberger Allee (tram M6). At Springpfuhl, the line is joined by the S7 from Ahrensfelde. Springpfuhl station, on the Allee der Kosmonauten (tram M8), probably needs a second island platform.
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The Biesdorfer Kreuz is the junction between the BAR, and the former Preussische Ostbahn to Königsberg. With the loss of Prussia east of the Oder, that line lost its original significance. It carries only regional services to Kostrzyn, just across the Oder. (The proposed high-speed line to Riga would use its alignment).
At the Biesdorfer Kreuz, the S7 and S75, turn toward central Berlin, using the tracks of the S5. The S5 itself runs alongside the Preussische Ostbahn, as far as Strausberg. The S-Bahn tangent line should allow interchange with the S5, and with the regional services to Kostrzyn. Here too, a station in the middle of the junction is inconvenient, and very difficult because of the track layout.
The solution is to re-route the S-Bahn, over a length of 3500 m, between Springpfuhl S-Bahn station and Biesdorf-Süd U-Bahn station. The new line would run on viaduct alongside the Märkische Allee, with a station where it crosses the S5. At this point, the alignment of the S5 is only slightly curved, and this would allow a new station (between Freidrichsfelde-Ost and Biesdorf). This station would also serve the adjoining retail cluster at Märkische Spitze (Mediamarkt). There would be another station at the crossing with Alt-Friedrichsfelde.
The new alignment would pass the edge of a low-density housing area, with limited demolition. It would rejoin the BAR near the crossing with U-Bahn line 5, which is on the surface here. A station above the U-Bahn tracks would connect to Biesdorf-Süd station, 150 m to the east.
The S-Bahn tracks would run alongside the BAR to Wuhlheide, on the main line to Poland. A new viaduct would improve the alignment, avoid a level crossing and junction tracks, and allow interchange with the S-Bahn line S3 to Erkner.
From the junction at Wuhlheide, to the next junction Grünauer Kreuz, the BAR is used by regional services, without intermediate stations. There is therefore no connection to line S47, which ends at Spindlersfeld station, about 150 m from the BAR tracks.
The new S-Bahn tracks could follow the BAR on this section. The logical station locations between Wuhlheide and Grünauer Kreuz, are Oberspreestrasse (adjacent to Spindlersfeld station), Glienicker Strasse, and possibly at the Teltow Canal. After the Grünauer Kreuz, trains would use the existing S-Bahn line to the airport (S45 and S9). At the Grünauer Kreuz, the BAR crosses the Görlitzer Bahn, the main line south-east from Berlin, and the parallel S-Bahn lines S8 and S46 to Zeuthen and Königs Wusterhausen.
The complicated track layout makes an interchange station at the Grünauer Kreuz very difficult, but that was the official planning (at least the initial DDR plans). A station here may not be necessary. West-to-north journeys can use the S9, and from Köpenick toward Schöneweide and Adlershof there are tram lines. From the airport toward Königs Wusterhausen (west-to-south), there will be regional services. Interchange from the tangent line to the south-east, can be provided by an additional curve to Grünau station. That would allow an additional service, on the most built-up section – for instance Marzahn – Grünau.
A large-scale alternative for this section would be, to route the S-Bahn in tunnel under central Köpenick, parallel to the BAR but about 1 km further east. That depends on the local geology: the line would cross the Spree and the Dahme. The alignment shown for that option (white dotted line) is indicative only.
Both alignments will cross the Görlitzer Bahn, and join the existing S-Bahn line to Schönefeld airport station. It has a separate alignment through Altglienicke and Grünbergallee stations: it rejoins the BAR alignment, 500 m east of Schönefeld station. An additional station was planned at Bohnsdorfer Chaussee.
East of Schönefeld station, the S-Bahn extension into the new airport is under construction. At first it runs alongside the BAR, then it makes a U-turn into the new terminal. (The long U-turn avoids a tunnel under the northern runway).
The line would be about 54-55 km long, from Oranienburg to Schönefeld station. The extension to the new terminal is almost 8 km long, giving a total length of about 63 km. That would be the longest S-Bahn line in Berlin, but still shorter then some lines of the S-Bahn Rhein-Ruhr.