At the western edge of Berlin, an improved rail service from Nauen to Potsdam would improve regional connections. In combination with a new rail service Nauen – Oranienburg, and a western link into Nauen from the Hannover line, it would create a new regional rail junction. At present there are limited tangential services: the regional lines RB20 Oranienburg – Potsdam, and RB21 Nauen – Potsdam.
The service requires some new infrastructure: a new link Nauen – Wustermark (replacing the old link line via Bredow), and improvements to the junctions at Wustermark and Golm. Most of the route is via the existing outer ring line, the Berliner Aussenring, BAR. With more intensive regional services, it might need extra tracks. The double-track line into Potsdam Hauptbahnhof also needs extra capacity, but that is not considered here.
This project is related to earlier proposals for new rail infrastructure north of Berlin, and it would connect to the proposed S-Bahn Teltow – Potsdam and the proposed new line to Berlin-Brandenburg airport.
A fast line to Berlin-Brandenburg Airport…
On the other side of Berlin, a new east tangent S-Bahn line was proposed here earlier. Both are tangential infrastructure along the BAR, but on the eastern side it lies inside the built-up area, where an S-Bahn line is appropriate. On the west side of Berlin, the BAR runs through an agricultural region, with small villages.
New infrastructure, Nauen and BAR
Nauen is 35 km from central Berlin, on the main line to Hamburg. The new link line would start east of Nauen station, and run partly parallel to the main Berlin road (Bundesstrasse 5). That would allow a better junction with the Lehrter Bahn at Wustermark. The link itself would be 8 km long, but it would shorten the total route length, compared to the old link line via Bredow.
The ‘Lehrter Bahn’ is the main line to Hanover, and northwestern Germany. (Lehrte itself is a junction, 15 km east of Hannover). The section between Spandau and Wolfsburg was reconstructed as a high-speed line (HSL). The remaining regional trains use a separate track, except for one section halfway between Berlin and Stendal. At Wustermark, the fast tracks are on the north side, and the new link would cross them west of the station. To allow room for the junction, the station (a simple island platform) could be moved west, to the Zeestower Strasse.
The new link line can do more than carry a service to Potsdam. In effect, it makes extra tracks available, from Nauen into Spandau, allowing better segregation of traffic. It would be logical to route freight from the Hamburg line over the link, and also interregional services running through to Spandau. It could also be used by trains from a new Brandenburg – Nauen link.
East of Wustermark station, the line to Spandau crosses the BAR, at the Wustermark junction. It first crosses the Havel Canal: this section would need a fourth track, with a new bridge over the canal. The Spandau line then passes under the Berlin ring motorway and Bundesstrasse 5. The BAR connecting track diverges before the ring motorway: it is also the access track to the freight yard at Elstal (officially ‘Wustermark’). This single-track curve would be doubled, with grade-separated junctions at both ends (from Wustermark and onto the BAR). This is difficult, because the improved link would twice cross Bundesstrasse 5. An underpass under the BAR tracks (in blue), is probably the best option.
There was once a halt on the ring line at Elstal. The village is small, and it has a station on the Spandau line anyway, but there is now a large Factory Outlet Center between the BAR and the village. A new station would be possible south of the former halt, on the re-routed Berliner Allee.
The stations at Priort and Marquardt serve small villages. Golm, on the other hand, is at the edge of Potsdam, one of the few cities in the former DDR with a growing population. Potsdam University has a new campus opposite the station.
South of Golm station is the BAR junction with the main line to Brandenburg and Magdeburg. Again the connecting curve is single-track: it should be grade-separated on the north side (from Golm), probably with a flyover. The other end already has an over-bridge, which simplifies the construction of a grade-separated junction there.
East of Sanssouci station, there are three tracks, with room for an extra track. The remaining 3 km, from there to Potsdam Hauptbahnhof form a bottleneck. Track capacity at the station is sufficient, but new reversing tracks are needed on the eastern (Berlin) side. The station has interchange with the S-Bahn line S7 to Berlin, other regional services, and Intercity services (suspended during construction work on the main line into Berlin).
The route Nauen – Potsdam, via the new link line, would be 34 km long. With seven intermediate stations, journey time should be about 30 minutes.