# Modeling High-Speed Rail for Germany

I’ve used a ridership model to construct a proposal for American high-speed rail – but what about the country I live in? There’s an election this year and one of the contested issues is climate change, and with growing passenger rail advocacy, it’s not outside the realm of possibility that there will be a large federal investment in dedicated high-speed lines (“NBS”). So I think it’s useful to model what German intercity rail will look like if there is greater investment in NBSes, culminating in a nationwide network such that ICEs will spend nearly all the time on NBSes or occasionally heavily upgraded legacy lines (“ABS”) rather than on slower lines.

If anything, I’m more optimistic about this network on the 15-year horizon than about American high-speed rail. Germany is slowly building more lines, like Stuttgart-Ulm, with Ulm-Munich, Frankfurt-Mannheim, Hanover-Bielefeld, and Frankfurt-Fulda on the horizon. People are also studying the prospects of a more expansive map as part of Deutschlandtakt additions, but unfortunately many 200 km/h ABSes are considered good enough even if they’re in easy terrain for a 300 km/h NBS, like Berlin-Halle/Leipzig.

The model

The professional way to model ridership is to split the travel zone, in this case the entire country, into very small pieces. I’m instead going to use an approximation with metropolitan areas and divisions thereof. For an illustration of my model’s level of sophistication, see below:

The gravity model to use is approximately,

$\mbox{Ridership} = \mbox{Pop}_{A}^{0.8}\cdot\mbox{Pop}_{B}^{0.8}/\mbox{distance}^{2}$

The justification for the exponent 2 in the gravity model is that the elasticity of ridership with respect to trip times appears to be close to -2. The justification for the exponent 0.8 is that it empirically appears true when considering Japanese cities’ Shinkansen ridership to Tokyo; the reason for this is that metropolitan areas comprise many different subsections, and the ones farther from city center have longer effective trip time counting connection time to the train station, and larger metropolitan areas tend to have longer distance from the center to the edge.

In the linked paper, the elasticity remains -2 even at short distances. However, we’re going to assume a minimum distance below which the elasticity vanishes, to avoid predicting infinite ridership as distance goes to zero. If distance is expressed in km, the best-fit constant is 75,000, with populations and annual ridership both in millions, and then if there’s no minimum distance, the model predicts Frankfurt (with 4 million people) to Mannheim (2.8 million, 75 km away) has 92 million annual riders just between the two regions, which is utter nonsense. In Japan, ridership looks like the floor is 500 km. In Germany, I’m going to round this to 2.5 hours, and because in practice it’s a bit more than 500 km, I’m going to round the constant 0.3/2.5^2 down to 1.8. We thus get,

$\mbox{Ridership} = 1.8\cdot\mbox{Pop}_{A}^{0.8}\cdot\mbox{Pop}_{B}^{0.8}/\mbox{max}\{2.5, \mbox{time}\}^{2}$

The network

This is the current draft of what I think Germany should build:

This isn’t too different from past maps I made. Berlin-Hanover is 60 minutes on this map and not 75 as on previous maps; a nonstop Velaro Novo can do it in 60 minutes, and the projected ridership is high enough that a half-hourly stopping train for service to Wolfsburg is viable in addition to a core express service. The branch point in the Rhine-Ruhr is moved to Dortmund, which slightly slows down service to Cologne and requires more tunnels, but improves frequency to the system massively, since Dortmund is a connection point to regional trains. Göttingen-Erfurt is dropped – all it does is connect Hanover and Hamburg with Erfurt, which is very small, and speed up travel to Nuremberg and Munich by 30 minutes, which is interesting but not enough to justify 100 km of high-speed rail.

Frankfurt still has an awkward-looking loop, whose purpose is to permit trains from Mannheim to enter the central tunnel to be constructed from the east and then run through to Cologne. However, this may not be necessary – trains from Cologne to Mannheim could just as well skip Frankfurt Hbf, serving Frankfurt at the airport or at a new station to be constructed at Frankfurt Süd, analogous to Cologne-Deutz for north-south through-trains. The expected traffic level is so high that the hit to Cologne-Frankfurt frequency is not awful, and the network complexity added by the skip isn’t higher than that added by having Frankfurt-Mannheim trains enter the tunnel from both directions depending on onward destination.

The network trip times are expressed in multiples of 15 minutes, with some places where timed connections are desirable, such as Fulda between Berlin-Frankfurt and Hamburg-Munich trains. However, overall, the traffic density predicted by the model is so high that on the stronger lines, like Cologne-Frankfurt, the timetable would not look like an integrated timed transfer system but rather the more continuous rapid transit-style model seen in Japan.

The power of polycentricity

The 0.8 exponent in the formula for ridership means that if we get to divide a single metropolitan area into subregions, then its ridership will increase. This is only justifiable if trains serve all such subregions; if the trains only serve some subregions, then we have to subtract them out. When we analyze New York or Tokyo, we can’t just add up each part of the metropolitan area separately – if we do so we must remove unserved sections like Long Island or Chiba, and the effect turns out to be similar to just lumping the metro area together.

However, in the Rhine-Ruhr, trains do serve nearly all sections of the region. The shape of the network there is such that intercity trains will continue stopping at Dortmund, Bochum, Essen, Duisburg, Wuppertal, Dusseldorf, and Cologne, at a minimum. The only recognizable centers without stops are Bonn and Mönchengladbach, and Bonn is connected to Cologne by streetcar.

Dividing cities and counties that are in the Rhine-Ruhr metropolitan region into the influence zones of the seven cities with stops based on what is the closest, we get Dortmund with 1.8 million, Bochum with 0.5, Essen 2, Duisburg 1, Wuppertal 0.9, Dusseldorf 2.3 (2 if we subtract out Mönchengladbach), and Cologne 2.9. Adding them up with exponents 0.8 is equivalent to considering a monocentric metropolitan core of 18.1 million; if we subtract out Mönchengladbach, it’s 17.6 million. This is enormous – larger than Paris and London, where only one high-speed rail stop is possible per train.

This also means we need to separately consider domestic and international traffic. Randstad is polycentric as well, and at a minimum there should be stops at Utrecht (1 million), Amsterdam (2.5), and Rotterdam (3.5), which means the region acts like a monocentric region of 9 million. The upshot is that if there were a 300 km/h train connecting Utrecht with Dusseldorf and Cologne with onward connections at both ends, and fares were st at domestic ICE rates and not Thalys rates, the connection between the two conurbations alone would generate about 17 million passengers a year. Of course, the model thinks all trip times up to 2.5 hours are equivalent, and the most distant city pair, Rotterdam-Dortmund, would be perhaps 1:45, but onward connections to German cities like Mannheim, Stuttgart, and Hanover are all 2:30 or longer with a 300 km/h Dutch line, and so there are benefits to constructing such a line over running at lower speed within the Netherlands.

To the extent the Frankfurt-Mannheim region can be thought of as a polycentric megaregion, the same is true there. Frankfurt, by which I mean Hesse-Darmstadt minus Bergstrasse, is 3.7 million people; Mainz is 0.6; the Rhine-Neckar (including Bergstrasse) is 2.4 million; Karlsruhe is 1.1 million; Stuttgart is 2.5 million. The model thinks that these regions combined generate 25 million annual trips to the Rhine-Ruhr.

# Zoomers Day Trip to Bielefeld on the ICE

2033-04-01

There’s a rite of passage every year in Berlin of taking a day trip to Bielefeld, an hour and a half away by ICE, every 10 minutes. The idea is to be able to retort to aging millennials who joke that Bielefeld does not exist than they’ve actually been there.

The Abitur is coming soon, and 12th-grade students are supposed to study, but Adam Mansour, Katja Brühl, Max Kleinert, and Nora Martinek are going in Bielefeld. It is not the best day to travel. Friday is a school day, even if it’s short enough it ended at 13:30, and it’s also a popular travel day so the tickets were a bit more expensive, and Adam had to convince his parents it’s worth spending 80€ and all the Germans do it. But at least today it means they don’t have to wake up at 7:00 tomorrow.

On the train going west, Katja keeps complaining about how the train bypasses Magdeburg because of 1980s-90s politics. She says she was looking for labor-related museums in Bielefeld but couldn’t find any; instead, she talks about how the mayor of Hanover is leading a red-black coalition and it’s not the SPD that she’s voting for in September or the SPD that subsidized childcare in Berlin that let her parents afford to have children.

The other three don’t find her annoying. Max and Nora come from much wealthier families, and Nora’s is scratching 10,000€/month, but when Katja talks about how thanks to education reforms pushed on the Länder by the Green-led federal government she could go to the same school as them, they don’t feel either attacked or guilty. They feel happy that they know her and Adam. They listen to what she says about Jusos and housing, the EU, feminism, or comprehensive schools, and it clicks with them because it’s their world too. They know that there are people who resent that the cities are growing faster and associate immigration with social problems; but they associate immigration with Adam’s parents, or with Nora, who only moved to Germany when she was five but who nobody ever calls an immigrant. Adam, in turn, does get called a Syrian immigrant, even though he was born in Germany, his parents having arrived just before the 2015 wave.

There are some American tourists on the train, talking about how pretty Germany is and how they wished the United States could have such a system. Max leans forward and says, “every time they’re on a train, they talk just about the train,” figuring circumlocutions because the Americans might recognize the German word Amerikaner and realize he is talking about them. Nora and Katja giggle, and Adam then joins too.

Otherwise, they try to distract themselves by talking about the exams and about university plans. All plan to go, and all have been told by teachers that they should get good enough grades to go where they want, but Max wants to study medicine and needs to get a 1.0 to get past the numerus clausus. “Do you want me to test you?” Adam asks him.

“Lol.”

They are all competitive about grades, even Katja, who told them once that neoliberal models of academic competition promoted inequality, and the Greens should do more to prevent what she calls the Americanization of German education. But Max told them when they planned the trip last week that he was treating it as his vacation day when he wouldn’t need to think about school.

Getting off the train, they start walking toward city hall; Bielefeld doesn’t have a bikeshare system, unlike Berlin, and bringing a bike on the ICE is not allowed. Adam insists on stopping on the way and taking detours to photograph buildings; most aren’t architecturally notable, but they’re different from how Berlin looks.

They run to the Natural History Museum and the Kunsthalle. The museum closes at 17:00 and they have less than an hour, then less an hour at the Kunsthalle until it closes at 18:00. They furiously photograph exhibits when they don’t have enough time to look at them and talk about them.

Adam is especially frantic at the archeology section, just because of the reminder of what he is giving up. He has read a lot of popular history and for the longest time wanted to go study it, but felt like he wouldn’t be able to get work with a humanistic degree and instead went for the real stream at school. When he met Katja two years ago he felt like this choice was confirmed – Katja for all her political interests is going to study environmental engineering and at no point expressed doubt about it.

Max spits on the Richard Kaselowsky memorial when the staff isn’t looking, distracted by other customers. In Berlin he might not even do this, but in Bielefeld he wouldn’t mind getting thrown out of a museum if worst came to worst. Nora and Adam didn’t know the history so as they go in he tells them Kaselowsky was a Nazi and so was the museum’s founder Rudolf Oetker, and the Oetker heirs had to return a few items that may have been stolen from Jewish owners in the Holocaust.

They find a döner place with good reviews and good falafel for Katja and are eating there. Normally they’d go out and get different things in Berlin, but Bielefeld is still a small city and even with Germany’s rapid immigration in the 2020s it doesn’t have Berlin’s majority-migration-background demographics.

Where they’re sitting overlooks the pedestrianized streets of the old city. There are some bikes, some pedestrians, some walking delivery drones. Berlin has a few of these zones within the Ring but they’re not contiguous and Bild accuses the Greens of promoting car-free zones for everyone except the federal government.

They talk about where they want to go, but Max and Katja are hesitant to publicly say what they feel about where they are. It’s Nora who openly says that she’s having fun and that Bielefeld definitely exists no matter what her parents say, but she wouldn’t want to live here. She doesn’t know if she wants to stay in Berlin – she wants to go to TU Munich, partly to see more places, partly because of some parental pressure to leave home – but Bielefeld feels a little too dörferlich.

They all laugh, and Adam says that judging by how his parents describe Daraa, it was a lot smaller than this. He says that they didn’t ever describe Daraa as especially lively, and always compared it negatively with Berlin when he was young and then eventually they just stopped talking about it, it stopped being important to them. Max and Katja nod and start comparing Bielefeld to parts of Germany they know well through extended family – Max’s father is from Münster and his mother’s family is in Göttingen and Hamburg, Katja’s parents are both from Berlin but her mother has family in Fürstenwalde.

And then somehow it drifts back to the election. Katja is worried the Union might win the election this time, stop free work migration, and freeze the carbon taxes at present levels. Adam doesn’t have family left in Syria but they have a few classmates who have family in India, in Vietnam, in Turkey. For the most part things are okay, but there’s always the occasional teacher or group of students who still think Neukölln and Gesundbrunnen are bad neighborhoods; they know who to avoid because people who are racist always find something negative to say to Adam specifically.

But for now, they have one another, and they have exams to score highly on to move on and go to university, and they have two hours to kill in Bielefeld until the ICE train they booked in advance departs to take them back home.

Robert Jackel asked me an excellent question in comments: what is a pulse? I’ve talked about timed transfers a lot in the last almost 10 years of this blog, but I never wrote a precise definition. This is a critical tool for every public transportation operation with more than one line, making sure that trains and buses connect with as short a transfer window as possible given other constraints. Moreover, pulse-oriented thinking is to plan capital investment and operations to avoid constraints that make transfers inconvenient.

When are pulses needed?

Passengers perceive the disutility of a minute spent transferring to be more than that of a minute spent on a moving vehicle. This is called the transfer penalty and is usually expressed as a factor, which varies greatly within the literature. In a post from 2011 I quoted a since-linkrotted thesis with pointers to Boston and Houston’s numbers, and in a more recent post I found some additional literature in a larger variety of places, mostly in the US but also the Netherlands. The number 2 is somewhere in the middle, so let’s go with this.

Observe that the transfer penalty measured in minutes and not in a factor is, naturally, larger when service runs less frequently. With a factor of 2, it is on average equal to the headway, which is why it is likely the number is 2 – it represents actual time in the worst case scenario. The upshot is that the value of an untimed transfer is higher the higher the frequency is.

I used the principle of untimed transfers and frequency to explain why small subway networks do not look like small bus networks – they have fewer, more frequent lines. Subway lines that run every 3-4 minutes do not need transfer timing, because the time cost of an untimed transfer is small compared to the likely overall trip time, which is typically in the 15-30 minute range. But the lower the frequency, the more important it is to time transfers. Thus, for example, Berlin times the U6/U7 transfer at Mehringdamm in the evening, when trains run every 10 minutes, but does not do so consistently in the daytime, when they run every 5.

But note: while the value of an untimed transfer is higher at higher frequency, the value of a timed transfer is the same – it is zero-penalty or close to it no matter what. So really, the relative value of timing the transfer decreases as frequency increases. But at the same time, if frequency is higher, then more passengers are riding your service, which justifies more investment to try to time the transfer. The German-speaking planning tradition is the most concerned with transfer timing, and here, it is done commonly at 10 minutes, occasionally at 5 minutes, and never that I know of at higher frequency.

Easy mode: one central station

If all your buses and trains serve one transit center, then a pulse means that they all run at the same frequency, and all meet at the center at the same time. This doesn’t usually happen on urban rail networks – a multi-line urban rail system exists in a high-ridership, high-frequency context, in which the value of serving a mesh of city center lines is high, and the cost of bringing every subway tunnel to one location is high. Instead, this happens on buses and on legacy regional rail networks.

The pulse can be done at any frequency, but probably the most common is hourly. This is routine in small American towns with last-resort bus networks serving people too poor or disabled to drive. Two and a half years ago a few of us on Transit Twitter did a redesign-by-Twitter of the Sioux City bus network, which has ten bus routes running hourly, all pulsing in city center with timed connections. A similar network often underlies the night buses of a larger city that, in the daytime, has a more complete public transport network, such as Vancouver.

Even here, planners should keep two delicate points in mind. First, on buses in mixed traffic, there is an upper limit to the frequency that can be timetabled reliably. The limit depends on details of the street network – Jarrett Walker is skeptical that timetabling buses that run every 15 minutes is feasible in a typical American city, but Vancouver, with no freeways within a city and a rich arterial grid, manages to do so every 12 minutes on 4th Avenue. A half-hourly pulse is definitely possible, and even Jarrett writes those into his bus redesigns sometimes; a 20-minute pulse is probably feasible as well even in a typical American city. The current practice of hourly service is not good, and, as I point out in the Sioux City post, involves slow, meandering bus routes.

The second point is that once the takt is chosen, say half an hour, the length of each roundtrip had better be an integer multiple of the takt, including a minimal turnaround time. If a train needs 5 minutes to turn, and runs half-hourly, then good times for a one-way trip from city center are 10, 25, 40, 55 minutes; if there is no turnaround at city center, for example if there is through-running, then half as many turnarounds are needed. This means that short- and long-term planning should emphasize creating routes with good trip times. On a bus, this means straightening meanders as needed, and either extending the outer end or cutting it short. On a train, this means speedup treatments to run as fast as necessary, or, if the train has a lot of spare time, opening additional infill stops.

The issue of branching

Branches and pulses don’t mix well. The ideal way to run a system with a trunk and branches is to space the branches evenly. The Berlin S-Bahn runs every 3-4 minute on the Stadtbahn trunk and on the North-South Tunnel, mixing services that run every 10 and 20 minutes at roughly even intervals. In such an environment, timed transfers in city center are impossible. This is of course not a problem given Stadtbahn headways, but becomes serious if frequency is sparser. A one-trunk, two-branch regional rail system’s planners may be tempted to run each branch every half hour and interpolate the schedules to create a 15-minute headway on the trunk, but if there’s a half-hourly pulse, then only one branch can participate in it.

This is visible when one compares S-Bahn and RegionalBahn systems. High-frequency S-Bahn systems don’t use timed transfers in city center, because there is no need. I can get from Jannowitzbrücke to Ostkreuz without consulting a schedule, and I would get to the Ring without consulting a schedule either, so there is no need to time the crossing at Ostkreuz. There may be sporadic transfer timing for individual branches, such as between the S9 branch of the Stadtbahn, which diverts southeast without serving Ostkreuz, and the Ring, but S9 runs every 20 minutes, and this is not a pulse, only a single-direction timed connection.

In contrast, RegionalBahn systems, running at longer ranges and lower frequencies, often tend toward timed transfers throughout. The tradeoff is that they don’t overlie to create high-frequency trunks. In some cases, trains on a shared trunk may even platoon, so that all can make the same timed transfer, if high trunk frequency is not desired; this is how intercity trains are run on the Olten-Bern line, with four trains to a platoon every 30 minutes.

Medium mode: dendritic networks

A harder case than the single pulse is the dendritic network. This means that there is a central pulse point, and also secondary pulse points each acting as a local center. All cases I am aware of involve a mainline rail network, which could be S-Bahn rather than RegionalBahn, and then bus connections at suburban stations.

Already, this involves more complex planning. The reason is that the bus pulse at a suburban station must be timed with trains in both directions. Even if planners only care about connections between the suburban buses and trains toward city center, the pulse has to time with inbound trains for passengers riding from the suburban buses to the city and with outbound trains for passengers riding from the city to the buses. This, in turn, means that the trains in both directions must arrive at the station at approximately the same time. A few minutes of leeway are acceptable, since the buses turn at city center so the connection always has a few minutes of slack, but only a few minutes out of what is often a half-hourly takt.

Trains that run on a takt only meet every interval equal to half the takt. Thus, if trains run half-hourly, they can only have suburban pulses every 15 minutes of travel. This requires planners to set up suburban pulses at the correct interval, and speed up or sometimes slow down the trains if the time between suburban nodes. Here is an example I’ve worked on for a Boston-Worcester commuter train, with pulses in both Framingham and Worcester.

Hard mode: meshes

The next step beyond the dendritic network is the multi-node network whose graph is not simply connected. In such a network, every node must have a timed transfer, which imposes considerable planning constraints. Optimizing such a network is an active topic of research in operations and transportation in European academia.

Positive examples for such networks come from Switzerland. Large capital investments are unavoidable, because there’s always going to be some line that’s slower than it needs to be. The key here is that, as with dendritic networks, nodes must be located at consistent intervals, equal to multiples of half the headway, and usually the entire headway. To make multiple timed transfers, trains must usually be sped up. This is why pulse-based integrated timed transfer networks require considerable planning resources: planning for rolling stock, infrastructure, and the timetable must be integrated (“the magic triangle”) to provide maximum convenience for passengers connecting from anywhere to anywhere.

# Density and Rail Transport (Hoisted from Social Media)

I wrote a long thread about regional rail and population density, and I’d like to explain more and give more context. The upshot is that higher population density makes it easier to run a rail network, but the effects are most visible for regional rail, rather than either urban rail or high-speed intercity rail. This is visible in Europe when one compares the networks in high-density Germany and low-density Sweden, and has implications elsewhere, for example in North America. I stress that high-speed rail is not primarily affected by background density, but only by the populations of cities within a certain range, and thus France, which has one of Western Europe’s lowest densities, manages to have high per-capita ridership on the TGV. However, the density of a regional mesh comes from background density, which is absent in such countries as France, Sweden, and Spain.

What is density?

Population density is population divided by area. This post is concerned with overall density at the level of an entire country or region, rather than the more granular level of the built-up urban area of a single city. What this means is that density is in large part a measurement of how close cities are to one another. In a high-density area like western Germany, Northern Italy south of the Alps, England, or the Low Countries, cities are spaced very close together, and thus people live at densities surpassing 300/km^2. In contrast, low-density areas have isolated cities, like Sweden, Australia, Canada, or the Western United States.

For example, take Stockholm. The region has about 2.5 million people, and has a strong urban and suburban rail network. However, there just aren’t a lot of cities near Stockholm. The nearest million-plus metro areas are Oslo, Gothenburg, and Helsinki, all about 400 km away, none much bigger than 1 million; the nearest 2 million-plus metro area is Copenhagen, 520 km away. The region I use as an example of German polycentrism, Rhine-Neckar, is about the same size as Stockholm, and has a good deal more suburban sprawl and car usage. The nearest million-plus region to Mannheim is Karlsruhe, 55 km away; it is a separate metropolitan area even though the Rhine-Neckar S-Bahn does have an hourly train to Karlsruhe. Frankfurt is 70 km away. A 400 km radius from Mannheim covers nearly the entirety of Germany, Switzerland, and the Low Countries; it reaches into Ile-de-France and into suburbs that share a border with Amsterdam. A 520 km radius covers Paris, Berlin, Hamburg, Milan, and Prague, and reaches close to Vienna.

Density and regional rail

Kaiserslautern is a town of 100,000 people, served by the Rhine-Neckar S-Bahn every half hour even though it is not normally seen as part of the Rhine-Neckar region. It has, in addition to the east-west S-Bahn, independent regional lines reaching north and south. When I visited two years ago, I saw these lines pulse while waiting for my delayed TGV back home to Paris.

This is viable because there are towns ringing Kaiserslautern, close enough that a low-speed regional train could connect them, with their own town centers such that there is a structure of density around their train stations. This in turn exists because the overall population density in Germany is high, even in Rhineland-Pfalz, which at 206/km^2 is slightly below the German average. The alternative structure to that of Germany would have fewer, larger cities – but that structure lends itself well to regional rail too, just with fewer, thicker lines running more frequently. If those smaller towns around Kaiserslautern did not exist but people instead lived in and right around Kaiserslautern, then it would be a city of about 400,000, and likewise Mainz might have 500,000 and the built-up area of Mannheim would have more people in Mannheim itself and in Ludwigshafen, and then there would be enough demand for a regional train every 10-20 minutes and not just every half hour.

I bring up Sweden as a low-density contrast, precisely because Sweden has generally well-run public transport. Stockholm County’s per capita rail ridership is higher than that of any metropolitan area of Germany except maybe Berlin and Munich. Regional rail ridership in and around Stockholm is rising thanks to the opening of Citybanan. Moreover, peripheral regions follow good practices like integrated intermodal ticketing and timed transfers. And yet, the accretion of a mesh of regional lines doesn’t really exist in Sweden. When I visited Växjö, which is not on the main intercity line out of Stockholm, I had a timed connection at Alvesta, but the timetable there and at Växjö looked sporadic. Växjö itself is on a spur for the network, but poking around the Krösatågen system it doesn’t look like an integrated timed transfer system, or if it is then Alvesta is not a knot. I was told in the replies on Twitter that Norrbotten/Västerbotten has an integrated network, but it runs every 2 hours and one doesn’t really string regional rail lines together to form longer lines the way one does in Germany.

Integrated regional networks

The integrated timed transfer concept, perfected in Switzerland, is ideal for regional and intercity networks that form meshes, and those in turn require high population density. With these meshes, regional rail networks overlap, underlaying an intercity network: already one can get between Frankfurt and Stuttgart purely on lines that are branded as S-Bahn, S-Bahn-like, or Stadtbahn, and if one includes RegionalBahn lines without such branding, the network is nationally connected. Even in Bavaria, a state with lower density than the German average, nearly all lines have at least hourly service, and those form a connected network.

It’s perhaps not surprising that Italy, which has high density especially when one excludes unpopulated alpine areas, is adopting German norms for its regional rail. As in Germany, this originates in urban networks, in Italy’s case that of Milan, but Trenord operates trains throughout Lombardy, most of whose population is not the built-up area of Milan, and even lines that don’t touch Milan run hourly, like Brescia-Parma. Italy is not unusual within Southern Europe in looking up to Germany; it’s only unusual in having enough population density for such a network..

Once the network is in place, it is obligatory to run it as an integrated timed transfer system. Otherwise, the connections take too long, and people choose to drive. This in turn means setting up knots at regular intervals, every 30 minutes for a mixed hourly and half-hourly system, and investing in infrastructure to shorten trip times so that major cities can be knots.

The concept of the knot is not just about regional service – high-speed rail can make use of knots as well. Germany has some low-hanging fruit from better operations and under-construction lines that would enable regularly spaced knots such as Frankfurt, then Mannheim, then Stuttgart, and far to the north Hanover and then Bielefeld. The difference is that Germany’s ideal high-speed rail network has around 20 knots and its existing regional rail network has about as many in Hesse alone. Nor can regional rail networks expect to get away with just building strong lines and spamming frequency on those, as the Shinkansen does – regional rail uses legacy alignments to work, generating value even out of lines that can only support an hourly train, whereas high-speed lines need more than that to be profitable.

Globally, the lowest-hanging fruit for such a system is in the Northeastern United States, followed by China and India. Population density in the Northeast is high, and cities have intact cores near their historic train stations. There is no excuse not to have a network of regional lines running at a minimum every 30 minutes from Portland down to Northern Virginia and inland to Albany and Harrisburg.

A few modifications to the basic Swiss system are needed to take into account the fact that the Northeast Corridor, run at high speeds, would fill a train every 5 minutes all day, and the core regional lines through New York could as well. But regional rail is not a country bumpkin mode of transportation; it works fine within 100 km of Frankfurt or Milan, and should work equally well near New York. If anything, a giant city nearby makes it easier to support high frequency – in addition to internal travel within the regional system, there are people interested in traveling to the metropole helping fill trains.

Low-density places absolutely can support good rail transport. But it doesn’t look like the German mesh. Two important features differ:

1. It is not possible to cobble together a passable intercity rail network from regional express lines and upgrade it incrementally. Intercity lines run almost exclusively intercity traffic. This tilts countries toward the use of high-speed rail, including not just France but also Spain and now Sweden. This does not mean high-density countries can’t or shouldn’t build high-speed rail – they do successfully in Asia, Italy has a decent network, Britain has high-speed rail plans, and Germany is slowly building a good network. It just means that high-density countries can get away with avoiding building high-speed rail for longer.
2. The connections between regional and intercity lines are simpler. Different regions’ suburban networks do not connect, and can be planned separately, for example by state-level authorities in Australia or provincial ones in Canada. These networks are dendritic: intercity lines connect to regional lines, and regional lines branch as they leave city center. Lines that do not enter the primary city center are usually weaker, since it’s unlikely that there are enough strong secondary centers at the right places that a line could serve them well without passing through the primary center.

In extreme cases, no long-distance rail is viable at all. Australia is a borderline case for Brisbane-Sydney-Melbourne high-speed rail – I think it’s viable but only based on projections of future population and economic growth. But Perth and Adelaide are lost causes. In the United States, railfans draw nationally-connected proposals, but in the Interior West the cities are simply too far apart, and there is no chance for a train to usefully serve Denver or Salt Lake City unless cars are banned. Connecting California and the Pacific Northwest would be on the edge of viable if the topography were flat, but it isn’t and therefore such a connection, too, is a waste of money in the economic conditions of the early 21st century.

Note that even then, cities can have suburban rail networks – Perth and Adelaide both have these, and their modal splits are about on a par with those of secondary French cities like Nice and Bordeaux or secondary American transit cities like Boston and Chicago. Denver is building up a light rail and a commuter rail network and one day these networks may even get ridership. The difference between the case of Perth or Denver and that of a German city is that Perth and Denver can rest assured their regional rail alignments will never be needed for intercity rail.

In less extreme cases, intercity trains are viable, and can still run together with regional trains on the same tracks. California is one such example. Its population density and topography is such that planning regional rail around the Bay Area and in Los Angeles can be kept separate, and the only place where intercity and regional trains could work together as in Germany is the Los Angeles-San Diego corridor. Blended planning with timed overtakes is still recommended on the Peninsula, but it’s telling that at no point have Bay Area-based reformers proposed a knot system for the region.

Those less extreme low-density cases are the norm, in a way. They include the Midwestern and Southern US, the Quebec-Ontario corridor, the Nordic countries, France, nearly all of Eastern Europe, and Southern Europe apart from Italy; this is most of the developed world already. In all of those places, regional rail is viable, as is intercity rail, but they connect in a dendritic and not meshlike way. Many of the innovations of Germany and its penumbra, such as the takt and the integrated intermodal plan, remain viable, and are used successfully in Sweden. But the exact form of regional rail one sees in Germany would not port.

# Electronics Before Concrete, not Instead of Concrete

The Swiss slogan electronics before concrete, and related slogans like run trains as fast as necessary, not as fast as possible, is a reminder not to waste money. However, I worry that it can be read as an argument against spending money in general. For many years now, Cap’n Transit has complained that this slogan is used to oppose bad transit like the Gateway Tunnel and if the money is not spent on public transportation then it may be spent on other things. But in reality, the Swiss slogans, all emphasizing cost minimization, must be reconciled with the fact that Switzerland builds a lot of concrete, including extensive regional rail tunneling in Zurich and intercity rail tunneling. Electronics precedes concrete, but does not always substitute for it; it’s better to think of these planning maxims as a way to do more with a fixed amount of money, and not as a way to do the same amount of project with less money.

The extent of tunneling in Switzerland

Here is a list of tunnels built in Switzerland since the 1980s, when its modern program of integrated timetable-infrastructure-rolling stock investment began:

This is not a small program. Zurich and Geneva are not large cities, and yet they’ve build regional rail trunk tunnels – and Zurich has built two, the most of any German-speaking country, since Berlin and Hamburg only have one of their trunk lines each in tunnel, the rest running above ground. The Mattstetten-Rothrist line likewise does not run at high speed, topping at 200 km/h, because doing so would raise the cost of rolling stock acquisition without benefiting the national integrated timetable – but it was an extensive undertaking for how small Switzerland is. Per capita, Switzerland has built far more intercity rail tunnels by length than France, and may even be ahead of Germany and Italy – and that’s without taking into account the freight base tunnels.

The issue of passenger experience

It’s best to think of organization-before-electronics-before-concrete as a maxim for optimizing user experience more than anything. The system’s passengers would prefer to avoid having to loiter 20 minutes at every connection; this is why one designs timed transfers, and not any attempt to keep the budget down. The Bahn 2000 investments were made in an environment of limited money, but money is always limited – there’s plenty of austerity at the local level in the US too, it just ends up canceling or curtailing useful projects while bad ones keep going on.

In Europe, Switzerland has the highest modal split for rail measured in passenger-km, 19.3%, as of 2018; in 2019, this amounted to 2,338 km per person. The importance of rail is more than this – commuters who use trains tend to travel by train shorter than commuters who use cars drive, since they make routine errand trips on foot at short distance, so the passenger-km modal split is best viewed as an approximation of the importance of intercity rail. Europe’s #2 and #3 are Austria (12.9%) and the Netherlands (11.2%), and both countries have their own integrated intercity rail networks. One does not get to scratch 20% with a design paradigm that is solely about minimizing costs. Switzerland also has low construction costs, but Spain has even lower construction costs and it wishes it had Switzerland’s intensity of rail usage.

Optimizing organization and electronics…

A country or region whose network is a mesh of lines, like Switzerland or the Netherlands, had better adopt the integrated timed transfer concept, to ensure people can get from anywhere to anywhere without undue waiting for a connecting train and without waiting for many hours for a direct train. This includes organizational reforms in the likely case there are overlapping jurisdictions with separate bus, urban rail, and intercity rail networks. Fares should be integrated so as to be mode-neutral and offer free transfers throughout the system, and schedules should be designed to maximize connectivity.

This should include targeted investments in systems and reliability. Some of these should be systemwide, like electrification and level boarding, but sometimes this means building something at a particular delay-prone location, such as a long single-track segment or a railway junction. In all cases, it should be in the context of relentlessly optimizing operations and systems in order to minimize costs, ensure trains spend the maximum amount of time running in revenue service and the minimum amount of time sitting at a yard collecting dust, reduce the required schedule padding, etc.

Systemwide optimization invariably shows seams in the system. When Switzerland designed the Bahn 2000 network, there was extensive optimization of everything, but at the end of the day, Zurich-Bern was going to be more than an hour, which would not fit any hourly clockface schedule. Thus the Mattstetten-Rohrist line was born, not out of desire to run trains as fast as possible, but because it was necessary for the trains to run at 200 km/h most of the way between Olten and Bern to fit in an hourly takt.

The same is true of speed and capacity improvements. A faster, more reliable system attracts more passengers, and soon enough, a line designed around a train every 15 minutes fills up and requires a train every 10 minutes, 7.5 minutes, 6 minutes, 5 minutes, 4 minutes. An optimized system that minimizes the need for urban tunneling soon generates so much ridership that the tunnels it aimed to avoid become valuable additions to the network.

The Munich S-Bahn, for example, was built around this kind of optimization, inventing many of the principles of coordinated planning in the process. It had a clockface schedule early, and was (I believe) the first system in the world designed around a regionwide takt. It was built to share tracks with intercity and freight trains on outer branches rather than on purely dedicated tracks as in the older Berlin and Hamburg systems, and some of its outermost portions are on single-track. It uses very short signaling blocks to fit 30 trains per hour through the central tunnel in each direction. And now it is so popular it needs a second tunnel, which it is building at very high cost; area activists invoked the organization before electronics before concrete principle to argue against it and in favor of a cheaper solution avoiding city center, but at the end of the day, Munich already optimized organization and electronics, and now is the time for concrete, and even if costs are higher than they should be by a factor of 2-3, the line is worth it.

Electronics before concrete, not instead of concrete

Switzerland is not going to build a French-style national high-speed rail network anytime soon. It has no reason to – at the distances typical of such a small country, the benefits of running at 300 km/h are not large. But this does not mean its rail network only uses legacy lines – on the contrary, it actively builds bypasses and new tunnels. Right now there are plans for an S-Bahn tunnel in Basel, and for an express tunnel from Zurich to Winterthur that was removed from Bahn 2000. The same is true of other European countries that are at or near the frontier of passenger rail technology. Even the Deutschlandtakt plan, compromised as it is by fiscal austerity, by high construction costs, by a pro-car transport minister, and by NIMBYs, includes a fair amount of new high-speed rail, including for example a mostly fast path from Berlin to Frankfurt.

When you plan your rail network well, you encourage more people to use it. When you optimize the schedules, fare integration, transfer experience, and equipment, you end up producing a system that will, in nearly every case, attract considerable numbers of riders. Concrete is the next step: build those S-Bahn tunnels, those express bypasses, those grade separations, those high-speed lines. Work on organization first, and when that is good enough, build electronics, and once you have both, build concrete to make maximum use of what you have.

# Quick Note: Consumption and Production Theories of Berlin

I’ve periodically written about consumption and production theories of cities – that is, whether people mostly move to cities based on consumption or production amenities. The production theory is that what matters is mostly production amenities, that is, jobs, and this underlies YIMBYism. Consumption theory is that people move for consumption amenities, and, moreover, these amenities are not exactly consumption in the city, for example good health outcomes, but consuming the city itself, that is neighborhood-level amenities in which who lives in the city matters. The latter theory, for example promulgated by Richard Florida, is that jobs follow consumption amenities like gay bars, and not the other way around. It is wrong and production theory is right, and I’d like to give some personal examples from Berlin, because I feel like Berliners all believe in consumption theory.

The situation in Berlin

Berlin is an increasingly desirable city. After decades in which it was economically behind, the city is growing. Unemployment, which stood at 19% in 2005, was down to 7.8% last year. With higher incomes come higher rents, and because Berlin for years built little housing as there was little demand, rents rose, and it took time for housing growth to catch up; on the eve of corona, the city was permitting about 6 annual dwellings per 1,000 people, up from about 1 in the early 2000s.

This is generally attributed to tech industry growth. There are a lot of tech startups in the city. I don’t want to exaggerate this too much – Google’s biggest Germany office is by far Munich’s, and the Berlin office is mostly a sales office with a handful of engineers who are here because of a two-body problem. But the smaller firms are here and the accelerator spaces are very visible, in a way that simply didn’t exist in Paris, or even in Stockholm.

Berlin’s production amenities

I might not have thought that Berlin should attract so much tech investment. My vulgar guess would be that tech would go to cities with many preexisting engineers, like Munich and Stuttgart, or maybe to Frankfurt for the international flight connections. But Berlin does make sense in a number of ways.

English

The city is mostly fluent in English. Jakub Marian’s map has France 39% Anglophone and Germany 56%, which doesn’t seem too outlandish to me. But Paris seems in line with the rest of France, whereas in Berlin, service workers seem mostly Anglophone, which is not the case in (say) Mainz or Munich.

The global tech industry is Anglophone, and good command of English is a huge production amenity. Other English-dependent industries seem to favor Anglophone European cities as well, for example various firms fleeing Brexit moved their European headquarters not to Paris but to Amsterdam or maybe Dublin.

The capital

The federal government is here. This is not relevant to tech – the startups here don’t seem to be looking for lobbying opportunities, and at any case German lobbying works differently from American lobbying and firm-level proximity to the capital is unimportant. However, the government stimulates local spending, which has increased employment. The government’s move here has been gradual, with institutions that during division were spread all over West Germany slowly migrating to Berlin.

Good infrastructure

The quality of infrastructure in Berlin is very good. The urban rail network was built when Berlin was Western Europe’s third largest city, after London and Paris, and has even grown after the war because the West built U7 and U9 to bypass Mitte. This means that commute pain here is not serious, especially on any even vaguely middle-class income. Moreover, Berlin has benefited from post-reunification investment, including Hauptbahnhof and two high-speed rail lines.

Consumption theory and the counterculture

The queer counterculture that I am involved with in Berlin tells a different story. To hear them tell it, Berlin has a quirky, individualistic, nonconforming culture, unlike the stifling normality of Munich. Artists moved here, and then other people moved here to be near the artists, paying higher rents until the artists could no longer afford the city. This story is told at every scale, from Berlin as a city to individual neighborhoods like Prenzlauer Berg and Neukölln. A lot of the discourse about Berlin repeats this uncritically, for example Feargus O’Sullivan at CityLab/Bloomberg Cities writes about the cool factor and about gentrification of old buildings.

It is also a completely wrong story. This is really important to understand: nobody that I know in the sort of spaces that are being blamed for gentrification, that is the tech industry and its penumbra, has any interest in the counterculture. I go to board games meetups full of tech workers who are fluent in English and often don’t know any German, and they have no connections at all to the local counterculture. They interact with immigrant culture spaces, not with the 95%+ white counterculture as defined by queer spaces in Neukölln that complain about gentrification in a neighborhood undergoing white flight at the rate of postwar New York (compare 2019 data, PDF-pp. 25 and 28, with 2016, PDF-pp. 28 and 31). Occasionally there are crossovers, as when an American comedian hosted live standup in February and then there were tech workers and said American also interacts with the counterculture, but a standup comic is not why Berliners complain.

Nor do I find foreign tech workers especially interested in German minutiae comparing Berlin with Munich. By my non-German standards, Berliners already jaywalk at indescribably lower rates, and I gather that Munich is stuffier but that’s not why I’m here and not there, the rents and the language are.

We’re not even particularly oppositional to the counterculture. I personally am because seeing queer space after queer space host indoor events during corona without masks was a horrifying experience; I went to a queer leftist meetup in late October in which people huddled together maskless and I was the only one with a mask on, except for one trans Australian physicist who drank a beer and then masked after finished. But the rest? They don’t care, nor should they. The counterculture is not the protagonist or the antagonist of Berlin’s story; it’s barely a bystander. Consumption theory is just what it promotes in order to convince itself that it’s important, that it spreads ideas and not viruses.

# When Should Cities Separate Short- and Long-Range Commuter Rail?

There’s a big difference between the various regional rail proposals I’ve made for New York and similar examples in Paris and Berlin: the New York maps go a lot further, and incorporate the entirety of regional rail, whereas the RER and the Berlin S-Bahn both focus on shorter-range, higher-frequency lines, with separate trains for longer-range service, generally without through-running. A number of New York-area rail advocates have asked me why do this, often suggesting shorter-range alternatives. Yonah Freemark made a draft proposal many years ago in which through-running trains went as far as New Brunswick, White Plains, and a few other suburbs at that range, on the model of the RER. But I believe my modification of the system used here and in Paris is correct for New York as well as the other American cities I’ve proposed regional rail in.

The reason boils down to a track shortage making it difficult to properly segregate S-Bahn/RER-type service from RegionalBahn/Transilien-type service. These are two different things in Paris, Berlin, Hamburg, and Munich, and Crossrail in London is likewise planned to run separately from longer-range trains, but in Zurich and on Thameslink in London these blend together. Separate operations require four-track mainlines without any two-track narrows at inconvenient places; otherwise, it’s better to blend. And in New York, there are no usable four-track mainlines. Philadelphia and Chicago have them, but not on any corridor where it’s worth running a separate RegionalBahn, which is fundamentally a short-range intercity train, and not a suburban train.

Scale maps

Here is a map of the Berlin S-Bahn (in black) and U-Bahn (in red) overlaid on the New York metropolitan area.

The reach of the S-Bahn here is about comparable to the size of New York City, not that of the metropolitan area. Even taking into account that Berlin is a smaller city, the scope is different. Service to suburbs that are not directly adjacent to Berlin the way Potsdam is is provided by hourly RegionalBahn trains, which do not form a neat network of a frequent north-south and a frequent east-west line through city center.

Here is the same map with the Paris Métro and RER; a branch of the RER D runs off the map but not much, and the RER E branches going east, still within the map box, go further but only every half hour off-peak.

The Parisian Transilien lines are not shown; they all terminate at the legacy stations, and a few have frequent trunks, generally within the scope of the box, but they don’t form axes like the east-west RER A and north-south RER B.

So what I’m proposing is definitely a difference, since I’ve advocated for through-running everything in New York, including trains going from Trenton to New Haven. Why?

Four-track lines and track segregation

In most of Berlin, the infrastructure exists to keep local and longer-range rail traffic separate. The Stadtbahn has four tracks, two for the S-Bahn and two for all other traffic. The North-South Tunnel has only two tracks, dedicated to S-Bahn service; the construction of Berlin Hauptbahnhof involved building new mainline-only tunnels with four tracks. Generally, when the S-Bahn takes over a longer line going out of Berlin, the line has four tracks, or else it is not needed for intercity service. The most glaring exception is the Berlin-Dresden line – the historic line is two-track and given over to the S-Bahn, requiring intercity trains to go around and waste 20 minutes, hence an ongoing project to four-track the line to allow intercity trains to go directly.

In Paris, there are always track paths available. Among the six main intercity terminals, the least amount of infrastructure is four-track approaches, at Gare de Lyon and Gare d’Austerlitz, with two tracks given over to the RER and two to everything else. Of note, the entirety of the Austerlitz network has been given to the RER, as has nearly all of the Lyon network, which is why the lines go so far to the south. The other terminals have more: Saint-Lazare and Nord each have 10 tracks, making segregation very easy. Only subsidiary regional-only stations have two-track approaches, and those are entirely given over to the RER, forming the eastern part of the RER A, the southern part of the RER B, and the western part of the RER C.

New York has a shortage of approach tracks. The reason for this is that historically the mainlines mostly terminated outside Manhattan, so the four-track approaches only went as far as Newark, Jersey City, etc. The LIRR has a four-track mainline into Penn Station from the east, which is why I’ve advocated for some segregation, but even that should eventually involve the express trains via East Side Access through-running to New Jersey; see the second map in this post.

On the New Jersey side there are plans for four tracks with new tunnels across the Hudson, but two tracks have to be shared with intercity trains, and there’s no easy way to neatly separate service into two S-Bahn tracks and two RegionalBahn tracks. In the short run, two of these tracks would have to include trains diverting west to the Morris and Essex Lines, which have a three-track main and therefore cannot segregate their own locals and expresses. In the long run, with the M&E system given its own tunnel across the Hudson, you could theoretically do two local and two express tracks, but that runs into a different issue, which is that east of Penn Station, there are two paths to New Rochelle, both of which have local stops.

The issue of having two paths between the city center station and an important suburban junction, both with local stations, is also a problem in London. North of the Thames, most mainlines are at least four-track, making segregation easy, hence the plans for Crossrail. The only exception is the Lea Valley lines. But in South London, lines are two-track – historically, railways that needed more capacity did not widen one line to four tracks but instead built a parallel two-track lines with its own local stations, often arranging the local stations in a loop. The result is a morass of merging and diverging lines reducing capacity, and London is only slowly disentangling it. In either case, it makes segregation difficult; Thameslink can’t just take over the slow lines the way Crossrail is, and therefore there are Thameslink trains going as far as Bedford and Brighton.

What does this mean?

It’s somewhat unusual for New York to get a regional rail network in which every train, even ones going to distinct cities like New Haven, is part of a central system of through-running. But it’s not unheard of – Thameslink works like this, so does the Zurich S-Bahn, and so does Israel’s national network with its Tel Aviv through-running – and it’s an artifact of a real limitation of the region’s mainline rail system.

But this should not be viewed as a negative. New York really does have suburban sprawl stretching tens of kilometers out. It should have suburban rail accompanying all these suburbs, and wherever possible, it should run on a schedule that is useful to people who are not just 1950s-style 9-to-5 commuters. Moreover, New York lacks either the vast terminals of Paris or the Ringbahn’s mushroom concept, which means trains from outer suburbs have nowhere to go but Manhattan, so they might as well be turned over into a through-running system.

# Regional Rail for Non-Work Trips

Good public transportation must be useful for all travel needs. This in particular includes trips that are not commutes to work, which are the most typical use case for suburban trains. This is a key difference between American and European public transportation: in some cases the modal split for work trips are similar, for example New York’s split is similar to that of the major German cities, but per capita ridership in the German cities is a lot higher than in New York, because off-peak service is better and people use it more for non-commute trips. In the linked post I went over this as a matter of better off-peak service; in this post I am going to go over the more fundamental question of, what kind of trips can regional public transport provide apart from work trips?

Some data from Germany

Germany periodically conducts surveys of transportation usage, called Mobilität in Deutschland, or MiD. The most recent was in 2017, and the one before it was in 2008. In Berlin, the data I have is from 2008, from the city’s transportation plan for 2030. On PDF-p. 30, it produces the following modal splits by trip type:

• Work: 39% transit, 40% car
• School: 31% transit, 31% car
• Shopping: 19% transit, 30% car
• Pleasure: 21% transit, 32% car
• Going back home: 27% transit, 31% car
• Other, including business: 25% transit, 67% car

Here is Hamburg, also as of 2008 and not 2017, on p. 7, with the city and suburbs listed separately:

• Work: 33%/48% city, 16%/65% suburbs
• School: 32%/13% city, 34%/30% suburbs
• Shopping: 11%/41% city, 4%/65% suburbs
• Errands: 21%/37% city, 4%/71% suburbs
• Pleasure: 17%/40% city, 5%/55% suburbs

The Hamburg S-Bahn barely extends past city limits, even less so than the Berlin S-Bahn, so the low suburban modal splits cannot be viewed as a failure of S-Bahn service to be useful for non-work trips. But it’s worth pointing out that in both Berlin and Hamburg (city, not suburbs), work is the activity with the highest modal split for public transport, followed by school.

Long and short trips

In a few posts over the years, I talked about a dichotomy of long and short trips. Long trips include the primary commute but also extraordinary trips such as to the airport; short trips are routine errands, including shopping and short-distance leisure trips.

In most transit cities, short trips are not done on transit but on foot. I usually bring up Asian examples because they concentrate development near the train station, so one walks to the train station either to shop at the department store within the station or to get on an actual train to get to work in city center. But this is equally true of Germany, even with vastly lower extents of transit-oriented development. The intersection points of the Ringbahn with U- and S-Bahn lines are replete with shopping centers.

The upshot is that if people don’t take regional trains to go shopping, because if the system works, then they can walk to retail. This is true even when retail is at big box scale – those Ringbahn stations have Kaufland and Real hypermarkets.

If regional rail is not for short trips, then what non-work trips is it for? The answer cannot be none, because ridership on S-Bahn trains in Berlin and Hamburg is too high compared with the work modal split. The answer can’t just be school either, because there aren’t vast numbers of school commuters.

Rather, it’s better to think in terms of sporadic and usual long trips. When I go play board games, it’s a long trip and not a short trip, because the community is citywide, and people come from Friedrichshain, from Charlottenburg, from far western suburbs, from Lichtenberg, from Pankow, from Schöneberg. The same is true of queer meetups – even when I lived in Neukölln and some of these meetups were walking distance to me, they were not walking distance to most attendees, who would take the U- or S-Bahn.

All of this falls under the rubric of sporadic long trips: long because they are not normally in-neighborhood, and sporadic because they are not one’s usual commute to work or school. But they often involve several roundtrips a week, producing healthy ridership at all hours of day.

Meetups are an example of using the train for socialization at a scale that’s expressly citywide or even regionwide. In that sense, a large city with a good regional transportation network is good for social connections, because it encourages communities to be more specialized to people’s interests. In a city the size of Berlin, even with Germany’s shocking lack of diversity, one can find enough queers for an English-language meetup. In a larger city like New York, without the same language load, one can even find ever more specialized communities – there is no one gaming community but many, and they intersect, for example one can look for queer gamers, or for a Harlem-based group with predominantly black demographics, and so on. This isn’t really any different from the economic advantages of large cities, which offer more division of labor.

The upshot is that even if the sort of travel one can do by regional rail that is not for work does not seem to exist in a city with poor off-peak public transportation service, this does not mean improving off-peak transit is pointless. On the contrary: over time, the existence of such service will let communities form at convenient locations based on the shape of the network. It will make the city bigger in a sense, and this is a good thing economically and socially.

# Building Depth and Window Space

How much window space does an apartment need, relative to its area, and how does this affect building style? A fascinating post from about a year ago on Urban Kchoze makes the argument that modern North American buildings are too deep – Simon calls them obese. Simon contrasts the typical building style in major cities in Europe and Asia with modern North American imitators and argues that the North American versions have too much ratio of floor area to exterior window width, which only works with loft-style apartments, which are not fit for families.

Is Simon correct? Not really. There’s an important feature of the block style in Europe that he’s missing. And this leads to an interesting observation by itself about area-to-window-width ratios.

The issue of building depth

Simon shows a bunch of satellite photos of buildings in a style called the euroblock. Here’s one example from Stockholm, in Södermalm:

The block has a width that looks like 14.6 meters. Midblock buildings have front windows overlooking the street and back windows overlooking a central courtyard; corner buildings overlook two streets. Either way, the area-to-frontage ratio is 7.3 meters. In general, buildings in Central Stockholm, urban Berlin, and Paris in average a depth of 13-14 meters, so the above typology would generate a ratio of 6.5-7 meters.

Simon contrasts this with American buildings. The euroblock typology is very uncommon in the US – New York’s typology is much less neat and liberally uses windows that overlook very narrow spaces. But it does exist, generally in higher-end recent developments. For example, here’s the Avalon East Norwalk, a condo project wedged between I-95 and the Northeast Corridor.

It has essentially the same built form as the euroblock. Its development history is of course different: there are no streets on the exterior, only parking lots, and it is a single project surrounding a big plaza with a swimming pool rather than many small buildings that together enclose a courtyard that comprises several separate gardens. But in terms of how the building looks from space, it’s similar. The width is 20 meters, for an area-to-frontage ratio of 10 meters, well above 6.5-7 meters.

However…

Euroblocks are complicated

The above Stockholm pic is a pretty simple building, conceptually: a linear building outlining the edge of a rectangle. This is not the typical euroblock; I had to look around Central Stockholm to find a fitting example. I could equally well use Hamburg or another such city of the same size class.

But in Paris, this form is almost unheard of, and in Berlin it is uncommon, I think mostly denoting postwar reconstruction. Paris and Berlin are larger cities, especially historically – in the Belle Epoque/Wilhelmine era, when this typology flourished, they were two of the largest few cities in the world, Berlin stagnating after World War Two and Paris growing exclusively in the suburbs. So they’d build up more of each lot and leave less unbuilt space between buildings. Instead, here is what a traditional Berlin block looks like, in this case in Neukölln:

These buildings enclose a central courtyard, as in Stockholm, but there the similarity ends. The courtyard is small, and there are several to a block. All these wings have internal corners with limited window space. Moreover, the wings that do not make it all the way to enclosing the courtyard, like the ones on the buildings north of Laubestrasse, have blank walls facing northeast, because they were built expecting the wing of another building to directly abut them. The wing of the building at the Laubestrasse/Elbestrasse eastern corner likewise has blank northeast-facing walls, and from space looks awkward, like a half-building. All of this was designed for more buildings, but some were never built or were knocked down.

If the euroblock has one big courtyard for the entire block as in the Stockholm and Norwalk examples, then the area-to-frontage ratio equals exactly half the building depth. But as soon as there are multiple courtyards, the ratio grows. The dimensions of the C-shaped building on Sonnenallee (one block south of Laubestrasse) just west of the corner building with which it shares the courtyard are 18 meters of street frontage by 38 of lot depth minus a half-courtyard of 11.5*12. This works out to 546 m^2/71 m, for a total ratio of 7.7 m, even though technically the building is never deeper than 13 m.

The blocks can get even more fractured. Here’s Prenzlauer Berg, in an area wedged between the former Wall and the Ringbahn:

The dimensions of the buildings fronting Korsörer Strasse on the north are pretty consistent. They all have an overall lot depth of about 32 meters, consisting of 14 meters of building, 11 meters of courtyard, and 7 meters of half-building with blank north-facing walls. The side wings are pretty consistently 7 meters deep each as half-buildings. Taking the pair of buildings flanking the second courtyard from the east as an example, they together are 35*32 minus 21*11, for 889 m^2/99 m = 9 m.

In Paris, building forms vary. But here is an example with wings, in the 17th:

The courtyards are smaller than in Berlin. Taking the second building from the west, we get 35*25 – 11*13, or 732 m^2/98 m = 7.5 m. When the courtyard is only about as wide as the building is deep, the above typology, similar to the image from Neukölln, generates a ratio equal to 5/8 the building depth, and not 1/2 as in the Stockholm example. The Prenzlauer Berg typology generates an even higher ratio, a full 2/3 of building depth if the courtyard is a square of side equal to the building depth.

And this matters. Buildings with simpler sides do get deeper in Paris. For example, this building in the 16th, wedged between two streets:

The depth of these buildings is 18 meters, so the area-to-frontage ratio is 9 m.

What does this mean?

My choice of the 16th and 17th in Paris for my examples is not random. Western Paris has been rich from the moment it urbanized – families of means choose to live this way. In general, within the family of euroblocks, the more desirable areas seem to have buildings with a slightly larger depth – the more working-class parts, such as Eastern Paris, have shallower buildings. Rich people would all else being equal prefer more window frontage space, but all else is not equal, and they prefer bigger apartments.

There is a definite limit on how deep buildings can be and how large the ratio of area to window frontage can be, but it is not as low as Simon posits. Ratios in the 8-9 region are not unheard of in old European buildings, and it stands to reason that euroblocks built in an environment of more prosperity, such as that of the early 21st century, could go slightly higher.

Moreover, the Norwalk example of a deeper building without wings is generally preferable to the traditional Berlin and Paris form of shallower buildings with wings. In Berlin, the apartments with street-facing windows are the most desirable. Historically, the wings were for the working class, which had to make do with narrow courtyards – sometimes narrower than today, the original statutory limit being less than 6 m wide due to 19th-century fire regulations. So the evolution of the euroblock is likely to be toward its American condo form.

# More on Station Costs

Talking to Marco Chitti about the history of Italian construction always fills me with hope. He’s been gathering data about metro construction in Milan and Rome, and told Elif, Eric, and me about the issue of building through constrained areas. Historic city centers are constrained because tunneling can damage buildings – the first two lines in Milan, built in the 1950s and 60s at abnormally low costs, caused some damage to buildings, since they involved cut-and-cover under streets only 12-15 meters wide. The good news is that tunneling with a tunnel boring machine is fine now. Stations remain an enormous challenge – but the conversation did fill me with optimism about future construction in cities that were not global imperial capitals 2,000 years ago.

TBM technology

Tunnel-boring machines have advanced to the point of being archeology-safe. Italian heritage protection laws from the 2000s forbid any risk to historic buildings and historic sites, but TBM technology at this point allows preserving artifacts. It involves injecting a gel ahead of the cutting edge, which is not supposed to be a cost-raiser.

The result is that tunneling is cheap. This is not a matter of low wages – in fact, Marco cites higher wages for Italian skilled workers who staff TBMs, up to €4,500 a month net, which rises to about €9,000 gross with social contributions. These are based on a nationwide scale that only weakly varies with location, which helps explain why Naples costs are not low despite the region’s low incomes.

Station construction

Station construction costs vary immensely by location. In Rome, on the same project, stations in a suburban part of the city might be €60-70 million. This does not mean construction is trivially easy: Rome’s suburbs still often host historic sites, having been home to patrician villas in Antiquity, and in fact the word suburb dates to that era. However, it’s relatively safe, and I don’t think Line C ran into such sites.

Then in the most constrained parts of the city, things are different. The extension plans for Line C deeper into city center have station costs in the €400-600 million range. This is not what things cost everything within Rome, or even everywhere within the densely-built parts of the city. But the Line C extension passes through the most historic sites. An already-under construction segment will go to the Colosseum, and a planned extension deeper into city center is to go to Piazza Venezia, at the Wedding Cake, and it is that station that is projected to cost €600 million.

The reason for the high cost is that it is not possible to do archeology- and building-safe cut-and-cover. Piazza Venezia doesn’t quite have enough room for a cut-and-cover dig of a full-length station. It is fed by a wide street, the Via Fori Imperali, and I asked Marco why not build cut-and-cover there, but he pointed out that the street goes through the historic Forum. It is in fact elevated over the ruins; any cut-and-cover there would endanger the Forum, and is not acceptable.

Without cut-and-cover, the only alternative is to mine the stations. Rome investigated the option of large-diameter TBMs on the Barcelona L9 model and found it infeasible, since the tunnels are so big they might themselves cause some building damage. Once the stations are mined from a small shaft, their costs explode. Second Avenue Subway built stations using the same method, and had similar per-station construction costs.

The good news

Mined station construction is in practically all cases not necessary. New Yorkers talk about the city’s high built-up density as a reason why costs are high. But in terms of actual stuff in the way of a tunnel, there’s less in New York than in Rome or Istanbul, which has even lower construction costs.

In fact, there is a line in Rome that is rather similar in urban geography to Second Avenue Subway: the Line B1 branch. It runs under a 27 meter wide street flanked by modern buildings that are about 9 stories tall above ground but also have underground parking, Italy having such a car culture that the middle class expects to own cars even in Rome. The cost: €527 million for 3.9 km, in 2010-15.

Moreover, the hard rock in New York should make it easier to build stations while maintaining building safety. Manhattan’s schist is brittle and therefore requires concrete lining, unlike the more uniform gneiss of Stockholm, famously forming natural arches that are pretty to look at from within the tunnels. However, it is still better soil for construction than the sand of Berlin’s U5 extension, to be opened next month, or the alluvial soil of Amsterdam.

The explanation Marco gives concerning station construction is physical and not institutional. This means it should transplant well into another setting – which it does!

In Berlin, the city-center U5 extension, including U55, is in today’s money around €240 million/km. The stations look like cut-and-cover to me, and if they’re not then it comes from severe NIMBYism since the line goes under the very wide Unter den Linden, but one of the stations is basically under the river and another is under U6 and involves moving the U6 station, and the sandy soil is genuinely bad to tunnel through. Suburban extensions in Berlin, with easy cut-and-cover stations, are consistently in the €100-150 million/km range, which is barely higher than the non-Forum Italian range. So Berlin looks fine, and just needs to invest resources into U- and S-Bahn extensions and not into extending the A 100 motorway.

Can New York have what Italy has?

Almost certainly! Second Avenue is not an old or narrow street by Italian standards. Nor are any of the other streets slated for subway construction in New York, such as Nostrand, Utica, and even 125th. Importing construction techniques from Italy and Germany should be feasible. There may be problems with local politics – New Yorkers absolutely hate admitting that another city may be better than theirs in any way, and this makes learning harder. But it is not impossible, and so far there do not seem to be any physical or economic obstacles to doing so.