What Berlin Should Be Building

A week and a half ago, I crayoned Berlin U- and S-Bahn expansion on video. With some tweaks, here is the final product:

Solid lines exist, dashed ones are under construction or (as far as I can tell) done deals, dotted ones are things that I am proposing or that are officially maybes; a few station names change to dissimilate different U- and S-Bahn stations and coname colocated stations

Here is the full-size version. (I know I’ve been asked to provide lighter JPGs, but my attempt at JPG compression turned 86 MB to 37 MB, hardly a coup de grâce.)

This is based on ongoing U-Bahn expansion plans plus the 2030 S-Bahn plan.


The most significant variation is that the dashed S-Bahn line from Gesundbrunnen to Hauptbahnhof and Potsdamer Platz, dubbed S21, is turned into a northwest-southeast trunk line in my plan, following a proposal by Felix Thoma in Zukunft Mobilität. The plan for S21 today is to stay north-south and link with Südkreuz and Schöneberg, beefing up frequency on the north-south S-Bahn.

I believe my routing to be superior, due to traffic on the Görlitzer Bahn, seen below (source, p. 6):

Currently, peak traffic on both the Stadtbahn and the North-South Tunnel is 18 trains per hour in each direction. This is low; Munich achieves 30 tph with very short signal blocks and more branching than Berlin has, splitting into seven branches on each direction rather than three or four. 30 is a limit value, but 24 is more common, and would substantially simplify operations.

The North-South Tunnel splits into a western branch, currently carrying S1 via Schöneberg to Wannsee every 10 minutes, and an eastern, carrying S2/S25/S26 via Südkreuz every 10/20/20 minutes; since the two branches have roughly equal ridership, each should run every 5 minutes, unlike today, where only Südkreuz gets such service. To the north, each of the two main branches can run every 5 minutes as well.

The Stadtbahn is asymmetric. Only 12 out of 18 tph continue west of Westkreuz: Spandau and Potsdam get 10-minute service, and in addition S5, turning at Westkreuz, runs every 10 minutes. As such, all growth in traffic on the western branches should be encouraged. This is thankfully already done, with expansion plans west of Spandau. To the east, traffic is the most overloaded, and will remain so even with the opening of the U5 extension last year. Going up from 18 to 24 maximum tph means 10-minute service on each of the four branches – S3 to Erkner, S5 to Strausberg-Nord, S7 to Ahrensfelde, S75 to Wartenberg (proposed to be extended into a loop going northwest). Today, S3 runs every 20 minutes, and S75 doesn’t run through but rather only runs from Warschauer Strasse east, and conversely, S9 curves from the Stadtbahn to the Görlitzer Bahn to the airport.

Rerouting S21 to connect to the Görlitzer Bahn means that trunk, currently carrying 18 trains per hour, can all run through to city center, and then either go to the Siemensbahn or loop from Hauptbahnhof to Gesundbrunnen. Such service also removes reverse-branching from the rest of the system, allowing all services to run more regularly and reliably since each of the four trunks, including the Ring, would run independently of the others, and delays wouldn’t propagate.


U-Bahn expansion in Berlin is mostly mothballed. The city prefers trams, even where they are inappropriate due to low speed over long stretches or forced transfers. Plans for U-Bahn expansion to Märkisches Viertel are uncertain, unfortunately. Plans for expansion to Tegel along a branch of U6 look dead, hence my resurrection of an older unbranched U5 extension; the current plan is to connect the Urban Tech Republic complex with the rest of the city via tram. Trams are cheaper but you get what you pay for; the ideal use of a tram is for cross-city routes, not primary routes to the center.

Hence various extensions that I think should be built. U7 to the airport looks like a done deal, and U7 to Staaken is favorable too, as is the low-cost, low-ridership one-stop extension of U3 to Mexikoplatz. U9 to Pankow and U2 to Pankow-Kirche are much-discussed, as is U8 to Märkisches Viertel, whose current cost/rider projection is favorable by international standards.

My additions are U1 extensions at both ends, the U5 extension to Tegel and then looping to intersect U6 and U8 in Reinickendorf, and the resurrection of the U10 plan as a U3 link (and not as a line to Steglitz, which gets extra S-Bahn service either way). The U1 extension to the west is forced to use cut-and-cover since the U1 tunnel under Kurfürstendamm is 1900s cut-and-cover, which is disruptive but cheaper than bored tunnel. The other two lines are long-term desires of the city and have been safeguarded for decades, with intersecting stations built to accommodate them.

Whether lines run in this configuration or another is up for debate. At Wittenbergplatz it’s easiest to link the new U10 system to U1 to Uhlandstrasse and then connect U3 to Krumme Linke with the existing Warschauer Strasse terminus. This would be an awkward system of U1, U2, and U3 in which the line going farthest north going east also goes farthest north going west and the line going farthest south to the east goes farthest south also to the west. If there’s a way to flip the situation, pairing U10 with present-day U1-west, U2-east with U3-west, and U3-east with U2-west, it should be done; this system in general has undergone many such changes over the generations.


  1. Eric2

    Is it worth switching the tails of U5 and U7 at Jungfernheide? Similar to what you suggest for U1/U2/U3.

    • Felix Thoma

      More complicated situation, because not situated just in level -1 below a street at a surface like Wittenbergplatz, and the U5 platform at Jungfernheide has already been built. But I guess there is an option for a track connection, so that Tegel could be operated as a branch of U7 first, for example.

      • Korot

        Platforms are already build, as the other half of the current side platforms (which would become island platforms), to allow for cross-platform interchange. There is even room for switches after the platforms. Though those switches would allow only that initial branch operation, not tail switching, because it’s not grade separated.
        But that concrete works would be similar to the works proposed at Wittenbergplatz for U1/2/3, but smaller and likely less disruptive (3 running U-bahns, vs 1).

    • Alon Levy

      Hmmm, maybe. The thing is, U7 is the weaker line since it misses city center, so the important thing is to set up a timed cross-platform transfer as at Mehringdamm.

      • Herbert

        What do you say about concerns that U7 might be getting too long to handle operatively?

  2. df1982

    Agree with all this, now do one for trams (and Regionalbahn while you’re at it).

    On a more serious note, the thing about the U-Bahn extensions is that apart from Märkisches Viertel (which should be done yesterday), they’re more in the nice to have category, rather than in the urgently build now category. It shouldn’t be an either/or thing with trams: Berlin conceives of them principally as high-capacity bus lines rather than low-capacity transit lines (like the tramways in Paris or certain Stadtbahnen in other German cities), and so new lines work well for corridors in the west where the buses are overloaded but that don’t merit upgrading all the way to U-Bahn levels of capacity. A good transport plan would invest in both modes.

    Some other thoughts:

    Would the “U10” to Hœhenschönhausen not be better off heading down Kniprodestraße (perhaps with an infill station on the Ringbahn) rather than Greifswalder Straße, to avoid duplicating the M4? The tram line runs pretty much entirely in a reserved corridor and can achieve some decent speeds, so there wouldn’t be much of a gain by a line that would essentially be undergrounding it.

    Also, it looks like there is a serious ridership imbalance on the Ring. Perhaps it warrants two lines running at 5min frequencies: one a pure circle (or a teacup doing Baumschulenweg-Neukölln-Ring-Neukölln), and one a tangential line doing Baumschulenweg-Bornholmer Straße via the eastern ring. This would also restore the Schönhauser Allee-Bornholmer Straße connection lost in your plan. Admittedly it might require work on extra platforms in places so it wouldn’t be an entirely painless addition.

    Finally, a thought on the U7 extension to BER: while on paper it looks like it could fall into the category of elite-projection-airport-connection transit projects, in fact I think it is a priority, not for the airport itself (which a bus from Rudow can handle), but for the airport station, which has major Intercity and Regionalbahn connections. Long distance travel would be significantly improved for people in that area, who wouldn’t have to backtrack to Südkreuz to change trains.

    • df1982

      Also it would be useful if you could do a schematic map of S-Bahn service, with notes on frequencies, because at the moment it’s all a big hodge-podge on the map.

    • Felix Thoma

      The problem with M4 is that it’s already quite busy, and extension to Leipziger Straße (see here today at 18:00: https://mein.berlin.de/projekte/strassenbahn-alexanderplatz-potsdamer-platzkultu-3/) will even make it more unstable. So I more and more support make it a metro corridor and instead build a tram along Kniprodestraße.

      I agree that U7 to BER could serve as a connection to short- and long-distance trains, perhaps even a high-speed line from Hbf. via Südkreuz and BER to Poland one day (my personal idea).

      • df1982

        Has everything been done to maximize capacity on the M4? In theory you could have coupled 33m trams running every two minutes, which comes close to the capacity of an U-Bahn running every 5 minutes. Not to mention a line down Kniprodestraße would probably wean some patronage away from Greifswalder Straße.

        • Eric2

          What exactly is the maximum frequency of a tram line? In all my years reading this blog I have never seen a good answer to that.

          • df1982

            There’s no fixed limit since trams run line of sight, but there are several limiting factors, including terminus capacity (loop or stub), traffic light sequencing, density of cross-traffic and tram length. Historically, networks were able to run up to a tram roughly every 20 seconds at peak periods, but this was with very short trams (the length of a standard bus) and generally only for short stretches in downtown before the lines would branch out.

            Today, Melbourne’s Swanson Street corridor achieves a tram roughly every minute at peak, over a stretch of about 3km (where eight lines merge), although most of the trams on this corridor are still quite short (and the stops are designed to take two or three at once) and the reliability is woeful, with severe bunching and frequent delays. I don’t think anywhere else in the world gets close to this: in fact the corridor will soon have a rail line built underneath it to cope with demand.

            On a modern system with longer trams you would probably struggle to maintain reliability at headways below 2 minutes, but I’d be happy to hear of counter-examples.

          • fjod

            Amsterdam gets (or used to get when I scraped this data a couple of years ago) 43 trams an hour, i.e. one every 1m23s, down Nieuwezijds Voorburgwal in the morning peak with 29-metre-long trams. It’s only a 800 metre stretch of street with three stops though, and all routes terminate at the northern end which I suppose limits bunching going south.

    • Herbert

      I’m a bit surprised U7 in this proposal doesn’t get a new stop at Schönefeld that isn’t the airport… Wouldn’t it be good to have a stop serving airport adjacent businesses and offices?

      • Alon Levy

        I believe this is the currently proposed stopping pattern? I added one city stop between Rudow and Rudow-Süd, but I don’t know to what extent there’s a serviceable edge city near the airport.

  3. michaelrjames

    Re image file size, I don’t know if I dare to give you a suggestion but here it is:
    (1) I downloaded the full file and saved it to my HD; it saved as a png file of 88MB.
    (2) I opened it in Adobe Acrobat (9). I find AA is very good at handling different formats and optimizing them for display and emailing etc. But when I saved what it had opened (nothing else done by me), I found that it had already reduced it to 8.1MB; looking at it at 100% magnification (cf. 6.8% to fit the whole map in the window) it looked as good as the original png. So it optimized it in the job of opening it.
    (3) I tried optimizing it using the Document/optimize scanned pdf, which I have found does a very good job on various formats imported into Acrobat (better than the “save as” options). However it actually increased file size (to about 10MB) so it must have optimally optimised it when it originally imported it. I didn’t keep this file any further. I also tried compressing it further using the “low” quality setting in the save-as step, but again it increased the file size–this time to 24MB–and the quality seemed unchanged compared to the 8.1MB file, so I abandoned this too.
    (4) I exported the 8.1MB pdf as jpeg; the resulting file remained at 8.1MB, and it opened ok in a jpeg viewer (Preview on Mac) and the image was perfectly acceptable at 100% (possibly the background map is fuzzier–not sure–but all the text was quite legible).

    So, the simple importation into Acrobat does what you need (and further optimizing doesn’t improve anything). You can probably use the pdf file itself but the exported jpeg (or png) files are similarly tenfold smaller without discernibly losing quality compared to the original 88MB file.
    The only catch here is that I have a full Adobe Acrobat (though an old version, 9) so I am not sure what can be done without it, ie. using other cutdown versions or pdf tools in other programs (I’m dreading moving to a new laptop which I will do in the next few weeks, because I am not going to pay thousands–or endless rental– for the full packages that are on my old work laptop).
    Hope that is a help.

  4. SB

    Why no extension of S3 from Erkner to Berlin Gigafactory? /s
    More seriously, doesn’t exentsion of S7 from Ahrensfelde to Werneuchen and taking over RB25 make sense?

    • Felix Thoma

      I agree that this should be analysed — there are advantages of regional rail (faster) and S-Bahn (more frequent, more stops served) however. And there are sometimes freight trains to Werneuchen, they would have to use S-Bahn tracks then, but there are a few freight trains that use S-Bahn tracks at some other places of the network as well.

  5. Eric2

    Worth noting that according to this map, many of Alon’s suggested metro extensions are already planned or extensively provisioned for.

      • Herbert

        Some of your crayons might have been proposed when Ernst Reuter was still alive…

  6. Onux

    I am always a fan of having the last stop on a subway line be at a S-Bahn/Regional Rail station, so that riders from the outer suburbs can more easily reach non-downtown parts of the city without traveling in then coming back out (this is not due to the number of such riders, which isn’t huge, but as a matter of sound network design and maximizing the usefulness of existing infrastructure).

    Your map seems to do this in some areas (extensions to Mexicoplatz, Pankow, Hohenschoenhausen) but what about Alt-Mariendorf to Marienfelde, Rhuleben to Stresow, or continuing U5 to Wittenau?

    To preempt a question, a connection just before the end rather than at the last stop (such as Wittenau vs Markisches Vitel for U8 on Alon’s map) satisfies my desired goal.

    • Felix Thoma

      I support U6 Alt-Mariendorf via S Marienfelde to Stadtrandsiedlung Marienfelde, connecting to U9 Steglitz via Lankwitz to S Marienfelde. Ruhleben should be to Spandau, there is already room for two tracks parallel to U7.

  7. Onux

    Would it be beneficial for Berlin to have a ring U-Bahn inside the Ringbahn (the UnterRing?). I am thinking continuing U1 Frankfurter Tor-Landsberger-Danzinger-Eberswalder-Bernauer-Nord Bf-Naturkunde-Hbf-Hansaplatz-Zoo-Wittenberg (drop Uhland and Kurfursten).

    Like any good ring every station except Landsberger would be a transfer (even if just to U3 in the south), it connects to every other U-Bahn (even U7) and every S-Bahn that enters the Ringbahn, and meets every U-Bahn through the central triangle (Unter den Linden, Alexanderplatz, and Stadtmitte) on both sides. The biggest miss is no connection to the south end of the Nord-Sud due to the lack of a station between Anhalter and Yorckestrasse, but that missed connection exists in the network currently.

    • Onux

      Small correction as I misread the map at first. With Alon’s new U3 across the city Prinzenstrasse and Schlesisches Tor would also be stations without a transfer.

    • fjod

      There is already a tram (M10) that runs almost exactly this route (stopping short at Lüneburger Straße) and it gets ridership of about 20 to 30 thousand on each interstation per workday per the document Alon posted. Within the ring, there is essentially nothing that receives a level of ridership this low except U4 and the section of U3 from Wittenbergplatz to Fehrbelliner Platz – though of course a faster u-bahn link will attract more people so this would end up a little higher.

      I also wonder if many journeys that would use this line are adequately served by the existing system already, either by tram (for short journeys), the ring or U5 (plus transfer if necessary). Also the line you propose would remove stops compared to the existing M10, making some journeys inconvenient – this is especially the case for the missed connection to trams at Prenzlauer Allee and the really long interstation you propose between Danziger Straße and Landsberger Allee. This would probably lower ridership.

      So in short, I feel there isn’t a case for this route, unless you believe the extension from Hauptbahnhof to Zoologischer Garten is going to massively raise ridership. But considering this section is paralleled by the Stadtbahn, this feels unlikely.

      • Herbert

        There are proposals to have an inner ring of trams again. If you look at the infrastructure, you can already see a sort of half ring…

        • fjod

          Yeah there’s a broader point, which I think Alon might have mentioned in the stream, that trams are actually good for circumferentials (my addition: especially inner ones). Passengers are going to be making short journeys so short stop spacing and being on the surface are desirable, and high frequency is also good because most people are going to use them for journeys with onward connections. I don’t really see what the point is of the southern part of that ring though, as the only seemingly reasonable route for it would be under U1/U3. Maybe you could go further south, but the settlement patterns, street layouts and bus ridership (per Alon’s document) don’t make this look particularly great – and also U7 fulfils some of that function anyway.

        • Alon Levy

          Yeah, and then the southern portion of this ring is already U1. Berlin can maybe extend M10 to Hermannplatz, but it would have to follow an awkward route via Kottbusser Tor, underneath U1 and above U8.

          • Onux

            I may not have been clear, my proposal was to turn U1 into the ring, by continuing north from Frankturter Tor and by connecting Wittenberg to the Zoo while dropping the last two western stations on U1 now.

  8. Onux

    Alon, you have written against reverse branches in the past, but wouldn’t Karower Kreuz to Wartenberg create a reverse branch starting at Hoen Nuendorf? Wouldn’t it be better to have S8 continue through Nord-Sud to access the core, rather than sending it even farther east than it does now?

    My apologies if I am misinterpreting your network design, as df1985 noted an S-Bahn schematic would be helpful.

    • Felix Thoma

      I rather propose a regional rail ring around Berlin (like Moscow Central Ring) perhaps incorporating the sections of S75 and S8 (which don’t go directly into the city center already now). Hohenschönhausen could be connected to the city center by U1, U5 or U9 extensions/branches.

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