Category: Regional Rail

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.

…leads to concrete

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.

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.

Sporadic long trips

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.

The German Way of Building Rapid Transit

Continuing my series on different traditions of building urban rapid transit, today it’s time for Germany and Austria, following the posts on the US, the Soviet bloc, Britain, and France. Germany had a small maritime empire by British and French standards and lost it all after World War 1, but has been tremendously influential on its immediate neighbors as a continental power. This is equally true of rapid transit: Germany and Austria’s rail traditions have evolved in a similar direction, influential also in Switzerland, Denmark, the Netherlands, and Belgium to varying extents.

S-Bahns and U-Bahns

Germany is one of the origins of urban regional rail, called S-Bahn here in contrast with the U-Bahn subway. The first frequent urban rail service in the world appeared in London in 1836, but trains ran every 20 minutes and the stop spacing was only borderline urban. Berlin in contrast innovated when it opened the east-west elevated Stadtbahn in 1882, running frequent steam trains with local spacing.

As elevated steam-powered urban rail, the Stadtbahn was not particularly innovative. New York had already been running such service on its own els going back to 1872. But the Stadtbahn differed in being integrated into the mainline rail system from the start. Berlin already had the Ringbahn circling the city’s then-built up area to permit freight trains to go around, but it still built the Stadtbahn with four tracks, two dedicated to local traffic and two to intercity traffic. Moreover, it was built to mainline rail standards, and was upgraded over time as these standards changed with the new national rail regulation of 1925. This more than anything was the origin of the concept of regional rail or S-Bahn today.

Vienna built such a system as well, inspired by many sources, including Berlin, opening in 1898. Hamburg further built a mainline urban rail connection between Hauptbahnhof and Altona, electrifying it in 1907 to become the first electrified S-Bahn in the world. Copenhagen, today not particularly German in its transportation system, built an S-Bahn in the 1930s, naming it S-tog after the German term.

However, German cities that built such S-Bahn systems would also build separate U-Bahn systems. U-Bahns in Germany have short stop spacing and tend to mostly serve inner areas: for example, on this map of Munich, the U-Bahn is in blue, and the trams are in red. Berlin has some farther-reaching U-Bahn lines, especially U7, a Cold War line built when the West got the U-Bahn and the East got the S-Bahn; had the city not been divided, it’s unlikely it would have been built at all.

Some of the early U-Bahns were even elevated, similarly to New York subway lines and a few Paris Métro lines. Hamburg’s operator is even called Hochbahn in recognition of the elevated characteristic of much of its system. Like Paris and unlike New York, those elevated segments are on concrete viaducts and not steel structures, and therefore the trains above are not very noisy, generally quieter than the cars at street level.

Light rail and Stadtbahns

The early els of Berlin and Vienna were called Stadtbahn when built in the 19th century, but since the 1960s, the term has been used to refer to mixed subway-surface systems.

Germany had long been a world leader in streetcar systems – the first electric streetcar in the world opened in Berlin in 1881. But after World War Two, streetcars began to be viewed as old-fashioned and just getting in the way of cars. West German cities generally tore out their streetcars in their centers, but unlike American or French cities, they replaced those streetcars with Stadtbahn tunnels and retained the historic streetcar alignments in outer neighborhoods feeding those tunnels.

The closure of the streetcars was not universal. Munich and Vienna retained the majority of their tram route-length, though they did close lines parallel to the fully grade-separated U-Bahn systems both cities built postwar. Many smaller cities retained their trams, like Augsburg and Salzburg, though this was generally more consistent in the Eastern Bloc, which built very little rapid transit (East Berlin) or severed itself from the German planning tradition and Sovietized (Prague, Budapest).

The Stadtbahn concept is also extensively used in Belgium, where it is called pre-metro; the Vienna U-Bahn and even the generally un-German Stockholm T-bana both have pre-metro history, only later transitioning to full grade separation. Mixed rapid transit-streetcar operations also exist in the Netherlands, but not in the consistent fashion of either the fast-in-the-center-slow-outside Stadtbahn or its fast-outside-slow-in-the-center inverse, the Karlsruhe model of the tram-train.

Network design

Rail network design in German-speaking cities is highly coordinated between modes but is not very systematic or coherent.

The coordination means that different lines work together, even across modes. In the post about France, I noted that the Paris Métro benefited from coordinated planning from the start, so that on the current network, there is only one place where two lines cross without a transfer. This is true, but there are unfortunately many places where a Métro line and an RER line cross without a transfer; the central RER B+D tunnel alone crosses three east-west Métro lines without a transfer. In Berlin, in contrast, there are no missed connections on the U-Bahn and the S-Bahn, and only one between the U-Bahn and S-Bahn, which S21 plans do aim to fix. Hamburg has two missed connections on the U-Bahn and one between the U- and S-Bahn. Munich has no missed connections at all.

But while the lines work well as a graph, they are not very coherent in the sense of having a clear design paradigm. Berlin is the most obvious example of this, having an U-Bahn that is neither radial like London or Moscow nor a grid like Paris. This is not even a Cold War artifact: U6 and U8 are parallel north-south lines, and have been since they opened in the 1920s and early 20s. Hamburg and Vienna are haphazard too. Munich is more coherent – its U-Bahn has three trunk lines meeting in a Soviet triangle – but its branching structure is weird, with two rush hour-only reverse-branches running as U7 and U8. The larger Stadtbahn networks, especially Cologne, are a hodgepodge of mergers and splits.


The German planning tradition has distinguishing characteristics that are rare in other traditions, particularly when it comes to fare payment – in many other respects, the Berlin U-Bahn looks similar to the Paris Métro, especially if one ignores regional rail.

Proof of payment: stations have no fare barriers, and the fare is enforced entirely with proof of payment inspections. This is common globally on light rail (itself partly a German import in North America) and on European commuter rail networks, but in Germany this system is used even on U-Bahns and on very busy S-Bahn trunks like Munich and Berlin’s; in Paris there’s POP on the RER but only in the suburbs, not in the city.

Unstaffed stations: because there are no fare barriers, stations do not require station agents, which reduces operating expenses. In Berlin, most U-Bahn stations have a consistent layout: an island platform with a stairway exit at each end. This is also common in the rest of the German-speaking world. Because there is no need for fare barriers, it is easy to make the stations barrier-free – only one elevator is needed per station, and thus Berlin is approaching fully wheelchair accessibility at low cost, even though it’s contemporary with New York (only 25% accessible) and Paris (only 3% accessible, the lowest among major world metros).

Fare integration: fares are mode-neutral, so riding an express regional train within the city costs the same as the U-Bahn or the bus, and transfers are free. This is such an important component of good transit that it’s spreading across Europe, but Germany is the origin, and this is really part of the coordination of planning between U- and S-Bahn service.

Zonal fares: fares are in zones, rather than depending more granularly on distance as is common in Asia. Zones can be concentric and highly non-granular as in Berlin, concentric and granular as in Munich, or non-concentric as in Zurich.

Monthly and annual discounts: there is a large discount for unlimited monthly tickets, in order to encourage people to prepay and not forget the fare when they ride the train. There are even annual tickets, with further discounts.

No smartcards: the German-speaking world has resisted the nearly global trend of smartcards. Passengers can use paper tickets, or pay by app. This feature, unlike many others, has not really been exported – proof-of-payment is common enough in much of Northern and Central Europe, but there is a smartcard and the fare inspectors have handheld card readers.

Verkehrsverbund: the Verkehrsverbund is an association of transport operators within a region, coordinating fares first of all, and often also timetables. This way, S-Bahn services operated by DB or a concessionaire and U-Bahn and bus services operated by a municipal corporation can share revenue. The first Verkehrsverbund was Hamburg’s, set up in 1965, and now nearly all of Germany is covered by Verkehrsverbünde. This concept has spread as a matter of fare integration and coordinated planning, and now Paris and Lyon have such bodies as well, as does Stockholm.

Germany has no head

The American, Soviet, British, and French traditions all rely on exports of ideas from one head megacity: New York, Moscow, London, Paris. This is not at all true of the German tradition. Berlin was the richest German city up until World War 2, and did influence planning elsewhere, inspiring the Vienna Stadtbahn and the re-electrification of the Hamburg S-Bahn with third rail in the late 1930s. But it was never dominant; Hamburg electrified its S-Bahn 20 years earlier, and the Rhine-Ruhr region was planning express regional service connecting its main cities as early as the 1920s.

Instead, German transportation knowledge has evolved in a more polycentric fashion. Hamburg invented the Verkehrsverbund. Munich invented the postwar S-Bahn, with innovations like scheduling a clockface timetable (“Takt”) around single-track branches. Cologne and Frankfurt opened the first German Stadtbahn tunnels (Boston had done so generations earlier, but this fell out of the American planning paradigm). Karlsruhe is so identified with the tram-train that this technology is called the Karlsruhe model. Nuremberg atypically built a fully segregated U-Bahn, and even more atypically was a pioneer of driverless operations, even beating Paris to be the first city in the world to automate a previously-manual subway, doing so in 2010 vs. 2012 for Paris.

There’s even significant learning from the periphery, or at least from the periphery that Germany deigns acknowledge, that is its immediate neighbors, but not anything non-European. Plans for the Deutschlandtakt are based on the success of intercity rail takt planning in Switzerland, Austria, and the Netherlands, and aim to build the same system at grander scale in a larger country.

The same polycentric, headless geography is also apparent in intercity rail. It’s not just Germany and Switzerland that build an everywhere-to-everywhere intercity rail system, in lieu of the French focus on connecting the capital with specific secondary cities. It’s Austria too, even though Vienna is a dominant capital. For that matter, the metropolitan area of Zurich too is around a fifth of the population of Switzerland, and yet the Swiss integrated timed transfer concept is polycentric.

Does this work?

On the most ridiculously wide definition of its metropolitan area, Vienna has 3.7 million people, consisting of the city proper and of Lower Austria. In 2012, it had 922 million rail trips (source, PDF-p. 44); the weighted average work trip modal split in these two states is 40% (source, PDF-p. 39). In reality, Vienna is smaller and its modal split is higher. Zurich, an even smaller and richer city, has a 30% modal split. Mode shares in Germany are somewhat lower – nationwide Austria’s is 20%, Germany’s is 16% – but still healthy for how small German cities are. Hamburg and Stuttgart both have metropolitan public transport modal splits of 26%, and neither is a very large city – their metro areas are about 3.1 and 2.6 million, respectively. Munich is within that range as well.

In fact, in the developed world, one doesn’t really find larger modal splits than these in the 2 million size class. Stockholm is very high as well, as are 1.5th-world Prague and Budapest, but one sees certain German influences in all three, even though for the most part Stockholm is its own thing and the other two are Soviet. Significantly higher rates of public transport usage exist in very large Asian cities and in Paris, and Germany does deserve demerits for its NIMBYism, but NIMBYism is not why Munich is a smaller city than Taipei.

To the extent there’s any criticism of the German rapid transit planning tradition, it’s that construction costs lately have been high by Continental European standards, stymieing plans for needed expansion. Märkisches Viertel has been waiting for an extension of U8 for 50 years and it might finally get it this decade.

The activist sphere in Germany is especially remarkable for not caring very much about U-Bahn expansion. One occasionally finds dedicated transport activists, like Zukunft Mobilität, but the main of green urbanist activism here is bike lanes and trams. People perceive U- and S-Bahn expansion as a center-right pro-car plot to remove public transit from the streets in order to make more room for cars.

The high construction costs in Germany and the slow, NIMBY-infused process are both big drags on Germany’s ability to provide better public transportation in the future. It’s plausible that YIMBYer countries will overtake it – that Korean and Taiwanese cities of the same size as Munich and Hamburg will have higher modal splits than Munich and Hamburg thanks to better transit-oriented development. But in the present, the systems in Munich and Zurich are more or less at the technological frontier of urban public transportation for cities of their size class, and not for nothing, much of Europe is slowly Germanizing its public transport planning paradigm.

Governance in Rich Liberal American Cities

Matt Yglesias has a blog post called Make Blue America Great Again, about governance in rich liberal states like New York and California. He talks about various good government issues, and he pays a lot of attention specifically to TransitMatters and our Regional Rail project for the Boston region, so I feel obliged to comment more on this.

The basic point Matt makes is that the quality of governance in rich liberal American states is poor, and as a result, people do not associate them with wealth very consistently. He brings up examples about the quality of schools and health care, but his main focus is land use and transportation: the transportation infrastructure built in New York, California, etc. is expensive and not of high quality, and tight zoning regulations choke housing production.

That said, I think there’s a really important screwup in those states and cities that Matt misses: the problem isn’t (just) high costs, but mostly total unwillingness to do anything. Do-nothing leaders like Charlie Baker, Andrew Cuomo, Gavin Newsom, and Bill de Blasio aren’t particularly interested in optimizing for costs, even the first two, who project an image of moderation and reason.

The Regional Rail proposal’s political obstacles are not exactly a matter of cost. It’s not that this should cost $4 billion (without the North-South Rail Link) but it was estimated at $15 billion and therefore there’s no will to do it. No: the Baker administration seems completely uninterested in governing, and has published two fraudulent studies making up high costs for both the North-South Rail Link and rail electrification, as well as a more recent piece of fraud making up high costs for Boston-Springfield intercity rail. The no comes first, and the high costs come second.

This history – no first, then high costs – is also the case for New York’s subway accessibility program. The MTA does not want it; the political system does not care either. Therefore, when disability rights advocates do force some investment, the MTA makes up high costs, often through bundling unnecessary investments that it does want, like rebuilding station interiors, and charging these projects to the accessibility account. A judge can force an agency to build something, but not to build it competently and without siphoning money.

I want to emphasize that this does not cover all cases of high American costs. Second Avenue Subway, for example, is not the result of such a sandbag: everyone wants it built, but the people in charge in New York are not competent enough to build it affordably. This does accord with Matt’s explanation of poor Northeastern and West Coast governance. But not everything does, and it’s important to recognize what’s going on.

The other important point is that these do-nothing leaders are popular. Baker is near-tied for the most popular governor in the United States with another do-nothing Northeastern moderate Republican, Maryland’s Larry Hogan. Andrew Cuomo’s approval rate has soared since he got 43,000 people in the state killed in the corona crisis.

People who live in New York may joke that the city has trash on the street and cockroaches in apartments, but they’re pretty desensitized to it. They politically identify as Democrats, and once corona happened they blamed Trump, as did many people elsewhere in the United States, and forgave Democrats who mismanaged the crisis like Cuomo. Baker and Hogan are of course Republicans, but they perform a not-like-the-other-Republicans persona, complete with open opposition to Trump, and therefore Massachusetts Democrats who have a strong partisan identity in federal elections are still okay with do-nothing Republicans. People who really can’t stand the low quality of public services leave.

Construction cost reform is pretty drastic policy, requiring the destruction of pretty powerful political forces – the system of political appointments, state legislators and mayors with a local rather than national-partisan identity, NIMBYs, politically-connected managers, the building trades, various equity consultants (such as many Los Angeles-area urbanists). They are not legally strong, and a governor with a modicum of courage could disempower them, but to be a moderate in the United States means to be extremely timid and technologically conservative. Matt himself understands that last point, and has pointed this out in connection with moderates who hold the balance of power in the Senate, like Joe Manchin and Susan Collins, but use it only to slightly shrink proposed changes and never to push a positive agenda of their own.

So yes, this is a construction cost crisis, but it’s not purely that. A lot of it is a broader crisis of political cowardice, in which non-leftist forces think government doesn’t work and then get elected and prove it (and leftists think real change comes from bottom-up action and the state is purely for sinecures, courtesy of the New Left). I warned in the spring that corona is not WW2 – the crisis is big enough to get people to close ranks behind leaders, but not to get them to change anything important. These states are rich; comfortable people are not going to agitate for the destruction of just about every local political power structure just to get better infrastructure.


I recently covered the Stadtbahn, a mode of rail transportation running as rapid transit (almost always a subway) in city center and as a tramway farther out. The tram-train is the opposite kind of system: it runs as a tramway within the city, but as rapid transit farther out. There’s a Human Transit blog post about this from 2009, describing how it works in Karlsruhe, which invented this kind of service pattern. Jarrett is bearish on the tram-train in most contexts, giving a list of required patterns that he says is uncommon elsewhere. It’s worth revising this question, because while the tram-train is not very useful in an American context, it is in countries with discontinuous built-up areas, including Germany and the Netherlands but also Israel. Israeli readers may be especially interested in how this technology fits the rail network away from the Tel Aviv region.

What is a tram-train?

Let’s dredge the 2*2 table from the Stadtbahn post:

Slow in centerFast in center
Slow in outlying areasTramwayStadtbahn
Fast in outlying areasTram-trainRapid transit

The terms fast and slow are again relative to general traffic. The Paris Métro averages 25 km/h, less than some mixed-traffic buses in small cities, but it still counts as fast because the speed in destinations accessed per hour is very high.

Be aware that I am using the terms Stadtbahn and tram-train to denote two different things, but in Karlsruhe the system is locally called Stadtbahn. German cities use the term Stadtbahn to mean “a tramway that doesn’t suck,” much as American cities call a dazzling variety of distinct things light rail, including lines in all four cells of the above table. Nonetheless, in this post I am keeping my terminology distinct, using the advantage of switching between different languages and dialects.

Tram-trains and regional rail

The Karlsruhe model involves trains running on mainline track alongside mainline trains, diverging to dedicated tramway tracks in the city, to connect Karlsruhe Hauptbahnhof with city center around Marktplatz. This also includes lines that do not touch the mainline, like S2, but still run with higher-quality right-of-way separation outside city center; but most lines run on mainline rail part of the way.

North American light rail lines, with the exception of the Boston, Philadelphia, and San Francisco Stadtbahn systems, tend to run as tram-trains, but never have this regional rail tie-in. They run on entirely dedicated tracks, which has two important effects, both negative. First, it increases construction costs. And second, it means that the shape of the network is much more a skeletal tramway map than the more complicated combination of an S-Bahn and a tramway that one sees in Karlsruhe. San Diego has a short segment sharing tracks with freight with time separation, but the shape of the network isn’t any different from that of other American post-1970s light rail systems, and there’s an ongoing extension parallel to a mainline railroad that nonetheless constructs a new right-of-way.

In this sense, the Karlsruhe model can be likened to a cheaper S-Bahn. S-Bahn systems carve new right-of-way under city center to provide through-service whenever the historic city station is a terminus, such as in Frankfurt, Stuttgart, Munich, or German-inspired Philadelphia. They can also build new lines for more expansive service, higher capacity, or a better connection to city center, like the second S-Bahn trunk in Hamburg; Karlsruhe itself is building a combined road and rail tunnel, the Kombilösung, after a generation of at-grade operation. The tram-train is then a way to achieve some of the same desirable attributes but without spending money on a tunnel.

It follows that the tram-train is best when it can run on actual regional rail tracks, with good integration with the mainline system. It is a lower-speed, lower-cost version of a regional rail tunnel, whereas the North American version running on dedicated tracks is a lower-cost version of a subway. Note also that regional rail can be run at different scales, the shorter and higher-frequency end deserving the moniker S-Bahn; the Karlsruhe version is long-range, with S1 and S11 reaching 30 km south of city center and S5 reaching 70 km east.

Where is a tram-train appropriate?

Jarrett’s 2009 post lays down three criteria for when tram-trains work:

  • The travel market must be small enough that an S-Bahn tunnel is not justified.
  • The destination to be served isn’t right next to the rail mainline.
  • The destination to be served away from the mainline is so dominant that it’s worthwhile running at tramway speeds just to get there and there aren’t too many people riding the line beyond it.

The center of Karlsruhe satisfies the second and third criteria. It is borderline for the first – the region has maybe a million people, depending on definitions, and the city proper has 312,000 people; the Kombilösung is only under-construction now and was not built generations ago, unlike S-Bahn tunnels in larger cities like Munich.

Jarrett points out that in the urban world he’s most familiar with, consisting of the United States, Canada, Australia, and New Zealand, it is not common for cities to satisfy these criteria. He does list exceptions, for example Long Beach, where the Blue Line runs in tramway mode before heading into Los Angeles on a mostly grade-separated right-of-way, whereupon it goes back into the surface in Downtown LA before heading into an under-construction tunnel. But overall, this is not common. City centers tend to be near the train station, and in the United States there’s such job sprawl that just serving one downtown destination is not good enough.

That said, the Long Beach example is instructive, because it is not the primary city in its region – Los Angeles is. I went over the issue of outlying S-Bahn tunnels a year ago, specifying some places where they are appropriate in Israel. The tram-train must be a key tool in the planner’s box as a cheaper, lower-capacity, lower-speed version of the same concept, diverging from the mainline in tramway mode in order to serve a secondary center. Karlsruhe itself is a primary urban center – the only time it’s the secondary node is when it connects to Mannheim, and that train doesn’t use the tramway tracks – but a secondary tram-train connection is being built in outlying areas there, namely Heilbronn.

Different models of urban geography

In the American model of urban geography, cities are contiguous blobs. Stare at, for example, Chicago – you’ll see an enormous blob of gray stretching in all directions. Parkland is mostly patches of green in between the gray, or sometimes wedges of green alternating with wedges of gray, the gray following commuter railroads and the green lying in between. Boundaries between municipalities look completely arbitrary on a satellite map.

In the German model of urban geography, it’s different. Look at Cologne, Frankfurt, Mannheim, or Stuttgart – the built-up area is surrounded by green, and then there are various suburban towns with parkland or farmland in between. This goes even beyond the greenbelt around London – there’s real effort at keeping all these municipalities distinct.

I don’t want to give the impression that the United States is the weird one. The contiguous model in the United States is also common in France – Ile-de-France is one contiguous built-up area. That’s how despite being clearly a smaller metropolitan region than London, Paris has the larger contiguous population – see here, WUP 2007, and see also how small the German and Dutch urban areas look on that table. Urban agglomeration in democratic East Asia is contiguous as in the US and France. Canada looks rather American to me too, especially Vancouver, the city both Jarrett and I are the most familiar with, while Toronto has a greenbelt.

This distinction moreover has to be viewed as a spectrum rather than as absolutes. Boston, for example, has some of the German model in it – there’s continuous urbanization with inner suburbs like Cambridge and Newton, but beyond Route 128, there are many small secondary cities with low density between them and the primary center. Conversely, Berlin is mostly American or French; the few suburbs it has outside city limits are mostly contiguous with the city’s built-up area, with the major exception of Potsdam.

The relevance of this distinction is that in the German or Dutch model of urban geography, it’s likely that a railway will pass through a small city rather far from its center, fulfilling the second criterion in Jarrett’s post. Moreover, this model of independent podlike cities means that there is likely to be a significant core, which fulfills the third criterion. The first criterion is fulfilled whenever this is not the center of a large metropolitan area.

It’s not surprising, then, that the Karlsruhe model has spread to the Netherlands. This is not a matter of similarity in transport models: the Netherlands differs from the German-speaking world, for examples it does not have monocentric S-Bahns or S-Bahn tunnels and it builds train stations with bike parking where Germany lets people bring bikes on trains. Nonetheless, the shared model of distinct municipalities makes tram-train technology attractive in South Holland.

Israel and tram-trains

In Israel, there are very few historic railways. A large share of construction is new, and therefore has to either swerve around cities or tunnel to enter them, or in a handful of cases run on elevated alignments. Israel Railways and local NIMBYs have generally preferred swerving.

Moreover, the urban layout in Israel is very podlike. There do exist contiguous areas of adjacent cities; Tel Aviv in particular forms a single blob of gray with Ramat Gan, Givatayim, Bni Brak, Petah Tikva, Bat Yam, and Holon, with a total population of 1.5 million. But for the most part, adjacent cities are buffered with undeveloped areas, and the cities jealously fight to stay this way despite extensive developer pressure.

The final important piece in Israel’s situation is that despite considerable population growth, there is very little rail-adjacent transit-oriented development. The railway was an afterthought until the Ayalon Railway opened in 1993, and even then it took until last decade for mainline rail to be a significant regional mode of transport. The state aggressively builds new pod-towns without any attempt to expand existing towns toward the railway.

The upshot is that all three of Jarrett’s criteria for tram-trains are satisfied in Israel, everywhere except in and around Tel Aviv. Tel Aviv is large enough for a fully grade-separated route, i.e. the already-existing Ayalon Railway. Moreover, because Tel Aviv needs full-size trains, anything that is planned to run through to Tel Aviv, even as far as Netanya and Ashdod, has to be rapid transit, using short tunnels and els to reach city centers where needed. A tram-train through Ashdod may look like a prudent investment, but if the result is that it feeds a 45 meter long light rail vehicle through the Ayalon Railway then it’s a waste of precious capacity.

But Outside Tel Aviv, the case for tram-trains is strong. One of my mutuals on Twitter brings up the Beer Sheva region as an example. The mainline going north has a station called Lehavim-Rahat, vaguely tangent to Lehavim, a ways away from Rahat. It could get two tramway branches, one diverging to the built-up area of Lehavim, a small suburb that is one of Israel’s richest municipalities, and the other to Rahat, one of Israel’s poorest. There are also interesting options of divergence going south and east, but they suffer from being so far from the mainline the network would look scarcely different from an ordinary tramway.

Beer Sheva itself would benefit from tramways with train through-service as well. The commercial center of the city is close to the train station, but the university and the hospital aren’t, and are not even that close to the subsidiary Beer Sheva North station. The station is also awkwardly off-center, lying southeast of the city’s geographic center, which means that feeding buses into it with timed transfers screws internal connections. So tramway tracks on Rager Boulevard, cutting off Beer Sheva North for regional trains, would do a lot to improve regional connectivity in Beer Sheva; intercity trains should naturally keep using the existing line.

In the North, there are similar examples. Haifa is not going to need the capacity of full-size trains anytime soon, which makes the case for various branches diverging into smaller cities to provide closer service in tramway mode strong. Unlike in Beer Sheva, the case for doing so in the primary center is weak. Haifa’s topography is the stuff of nightmares, up a steep hill with switchback streets. The mainline already serves the Lower City well, and climbing the hill is not possible.

This creates an interesting situation, in which the technology of the tram-train in the North can be used to serve secondary cities like Kiryat Ata and Tirat Carmel and maybe enter the Old City of Acre, but the operational pattern is really that of a Stadtbahn – fast through Haifa and up most of the Krayot, slow through smaller suburbs.

Job Sprawl as Deurbanization

A few years ago, Aaron Renn was writing, I think about the General Electric headquarters’ move from suburban New York to Downtown Boston in 2016, that in the future, city center jobs would go to high-value industries like corporate HQs and professional services, and then lower-end stuff like call centers would go in suburban office parks. At the time I didn’t understand the full meaning of this – I was still thinking of employment in a narrow city center of a few blocks rather than a broader region, like the 100 km^2 zone I use to compare the US with Canada and France because that’s the most granular data I have in the latter two countries. But in retrospect, Aaron was getting at a dangerous trend in which job markets deurbanize. This is not a new trend – office park sprawl goes back to the 1970s, and industrial sprawl even earlier – and to some extent it’s less about deurbanization and more about the urban job market reaching maximum size. But whatever the history of it, it’s a serious threat to economic performance – and the solution to it requires better public transportation.

Cities as job markets

I’ve written before about production theory. The only thing I have to add on the theory side is that since I wrote that post, I was at a talk that Alain Bertaud gave at Marron, about urbanization. The main topic of the talk was about urban growth and sprawl in the developing world, but at the beginning of the presentation, he gave some remarks about cities and corona. Zoom meetings like the one we had, he warned, were fine, but cities are fundamentally job markets that succeed through spontaneous interaction, and this spontaneity does not exist with remote work. This is to a large extent the new urban geography thesis of Paul Krugman or the work of Ed Glaeser – cities exist as places of production first, and this production requires close proximity.

Now, close proximity depends on technology. In a city with the transport technology of London circa 1800, close proximity means the scope of the City of London, and even 5 km is uncomfortably far. In a city with cars and highways, the distance is much greater – but it is not the same as commute distance. A half-hour drive is not spontaneous. When I asked American friends and coworkers about their productivity through the spring corona lockdowns, a Boston lawyer told me that lawyers wouldn’t even travel midday for clients for 20-30 minutes, since their time was too valuable – they’d schedule conference calls.

This does not mean that the entire work market has to be within such a short distance. It certainly helps, but different industries can cluster in different parts of the city. But there is a maximum distance within which the city is recognizably a single job market.

Aaron Renn’s bifurcation

Aaron talks about bifurcation a lot, between winners and losers. He relates the move of large corporate HQs to city centers to this bifurcation: city centers win by having higher-value added, higher-paying jobs, everyone else gets saddled with lower-end jobs. Moreover, these lower-end jobs are commodities – a call center can be anywhere – and therefore they compete on price and not quality, frustrating the attempt of any region on the margins of the US to climb up the value chain.

That said, even the sort of job sprawl of the 1970s, spearheaded by big companies’ move out of city centers to rich suburbs like GE to Fairfield and IBM to Armonk, represents the same threat to urban productivity. That was driven by snobbishness – the elite suburbanized, and then dragged jobs outside the city with it, for example GE did partly on spurious grounds of resilience in face of nuclear war destroying city centers. Today, the city gains higher-end jobs at the expense of the suburbs, the opposite of the situation in the 1970s. But the same situation of jobs outside one major core persists.

Is this polycentricity?

No. It’s become fashionable to speak of polycentric cities as the next evolution, to decongest old cores. But doing so requires the urban geography to have centers. I pointed out previously that Los Angeles may claim to be polycentric but is just weak-centered – the secondary centers have a few tens of thousands of jobs each at most. This is not like the big city centers one finds in Kyoto, Osaka, and Kobe, or even in the Rhine-Ruhr or Randstad.

Keihanshin, the Rhine-Ruhr, and Randstad are all agglomerations of historic cities. It is possible to also form polycentric regions out of new development – for example, Yokohama was founded as a 19th-century treaty port and then grew as a Tokyo suburb. Both New York and Paris have moved their central business districts by a few kilometers gradually, New York from Lower Manhattan to Midtown and Paris from Les Halles to around the Opera; both also have near-center business centers, like Long Island City or La Défense. Even then there’s likely to be some efficiency loss in decentralizing city center jobs this way, but it’s still easier to shuttle between Times Square and World Trade Center than between either and New Brunswick.

The public transit solution

In the 1970s, the abandonment of city centers was motivated by a desire to escape their poverty and a belief that the suburbs were the future. Urban poverty still exists but inner-urban wealth is considerable and increasing, and the belief that the suburbs were the future turned out to be incorrect – one cannot be a suburb of nowhere.

The model of suburbanization that can be sustained is one built from the late 19th century to about the 1950s and early 60s: jobs stay in the city, people go wherever.

Doing so requires three things: offices, dwellings, and a way of getting between them.

Offices mean commercial upzoning – some American cities are good about it, but the ones with the most demand, like New York, aren’t. In general there’s little appetite for commercializing near-center neighborhoods in the US, whereas Europe is looser about it and therefore new firms can sprout a few subway stops outside the primary center, for example Spotify two stops outside T-Centralen. Residences likewise require upzoning, especially for mid- and high-rise apartment buildings near subway stations where they exist and have capacity.

But in many cases, it’s required to also build up public transportation. Big central business districts feature hundreds of thousands of people converging on a small area at the peak, and the biggest go up into the millions. The highest-capacity form of transportation is required, which is rapid transit, never cars or surface transit.

Rapid transit and city centers are symbiotic, now as in 1910. An expansive rapid transit system, with high service quality, is required to serve city centers from multiple directions; and city centers are required to give people something to take the trains to, or else they’ll just drive everywhere and only take the train to the sports stadium or the airport.

And ultimately, city centers are required for economic efficiency, because of the importance of proximity for spontaneous economic and social interactions. Rapid transit also benefits from high efficiency – it’s very cheap to operate compared with the cost of car ownership. The alternative is a kind of deurbanization, in which people may live at high density relative to travel speeds but don’t form large clusters enabling the highest productivity.

Public Transportation in Megacities

I’ve been talking so much lately about integrated timed transfer in the context of Boston that people started asking me if it’s also applicable to New York. The answer is that the basic principles are not scale-dependent, but the implementation is, so in very large cities, public transport planning should not look like in Switzerland, a country whose largest metro area is staring at 2 million people from the bottom.

The one caveat here is that most cities are not huge. The developed world has seven megacities: Tokyo, Seoul, New York, Los Angeles, Osaka, London, Paris. And Los Angeles doesn’t really have public transportation, so we’re down to six. The middle-income world has a bunch more for sanity checking – Mexico City, São Paulo, Rio de Janeiro, Buenos Aires, Johannesburg, Moscow, Istanbul, Tehran, Beijing, Shanghai, Guangzhou, Shenzhen, Bangkok – but all are either still in convergence mode building up their networks or (mostly in Latin America) have given up. So much of this comes down to the idiosyncrasies of six cities, of which the largest three networks are substantially in the same planning tradition.

Demand is huge

Big cities have big centers, which can’t really be served by any mode except rapid transit. Even in Los Angeles, what passes for a central business district has around a 50% public transport modal split. This means that the transport network has to deliver high throughput to a relatively small city center. Even in a low-kurtosis city like Paris, most Métro lines converge on a narrow area ranging from Les Halles to Saint-Lazare; in a high-kurtosis one like New York or Tokyo, there are a few square kilometers with 200,000 jobs per km^2, which require an exceptionally dense network of rapid transit lines.

Some other network design principles follow from the need to amply serve city center. Specifically, high frequency is rarely a worry, because there’s so much demand even off-peak that usually megacity subway systems do not venture into the frequency range where long waits deter traffic; New York’s 10-minute midday gaps are bad, but that’s unusual and it comes from a combination of the legacy of postwar fear of subway crime suppressing demand and excessive branching.

But other principles require careful planning still.

Electronics before concrete, megacity version

The driverless lines in Paris support peak throughput of 42 trains per hour – a train every 85 seconds. CBTC on Line 13 without driverless operation supports 38 tph, and London’s CBTC-equipped lines support 36 tph when the branching isn’t too complex. It is imperative for other cities to learn from this and do whatever they can to reach similar headways. The difference between 21 tph, as in Shanghai, and Paris’s 42, is equivalent to building a brand new subway line. And what’s more, in a city in the size class we’re talking about, the primary concern is capacity – coverage is already good, so there really is no reason to build two 21 tph lines instead of one 42 tph one.

The situation in Paris is in a context with self-contained lines. That said, extremely busy self-contained lines do exist in other megacities – London has a bunch with near-Parisian levels of throughput, New York has some, Tokyo has a few, Seoul and Osaka are both more self-contained than Tokyo is.

Throughput and organization

The primacy of throughput means that it’s worthwhile to build small infrastructure upgrades, even with concrete, if they help with capacity. Right now the Northern line reverse-branches with the branches to the north recombining with those in the center, and Transport for London would like to split the line in two, reducing branching complexity, which would increase capacity. But doing so requires improving pedestrian circulation in the corridors of the branch point, Camden Town, where TfL expects very large transfer volumes if there’s a split and already there are circulation problems today without a split. Hence the plan in the medium term is to upgrade Camden Town and then split.

If there are bumper tracks at the end of a line, as at 8th Avenue on the L or Flushing-Main Street on the 7, then it’s useful to dig up the street for another block just to add some tail tracks. That way, trains could enter the station at full speed. This increases throughput, because the terminal interlocking has trains heading in opposite directions crossing each other at-grade, which imposes schedule constraints; it’s best if trains can go through the interlocking as fast as possible to reduce the time they’re in a constrained environment, but that in turn requires short tail tracks so that an overrun of a few meters is not catastrophic. Ideally the tail tracks should even extend a full train length past the platform to place the interlocking on the other side of it, as is done in Paris and Moscow; in that case, trains cross the interlocking out of service, when it’s easier to control their exact timings.

Such projects are disruptive, but the disruption is very localized, to just one transfer station for a deinterlining project as in London or one terminal as in New York, and the impact on capacity is very large, if not quite as large as the full suite of signaling and track upgrades that make the difference between a train every 3 minutes and a train every 1.5 minutes.

Network design

The ideal metro network is radial. Megacities already support that just because so many lines have to serve city center. However, it’s important to make sure every pair of lines intersects, with a transfer. No large metro network in the world achieves this ideal – Mexico City’s network is the largest without missed connections, but it is not radial and its only three radial lines are overburdened while the other lines have light ridership. Paris has just a single missed connection on the Métro proper, not counting the RER, but it has many pairs of lines that do not intersect at all, such as M1 and M3. London is more or less a pure radial, but there are a handful of misses, including one without any transfer between the two lines anywhere, namely the Metropolian line (including Hammersmith and City) and the Charing Cross branch of the Northern line.

Big cities that plan out a metro network have to make sure they do better. Missed connections reduce passenger ridership and lead riders to overload the lines that do get connections; for example, in Tokyo one reason cited for the high ridership of the Tozai Line is that until Fukutoshin opened it was the only one with a transfer to every other subway line, and in Shanghai, Line 1 was extremely congested as long as the alternatives going north either had critical missed connections (like Line 8) or avoided city center (like Line 3).

The role of regional rail

Regional rail as a basic concept is mostly scale-invariant. However, the design principles for trains that come every half hour are not the same as those for trains that come every 5 minutes. If trains come every half hour, they had better connect cities in a roundtrip time equal to an integer number of half hours minus turnaround times, so that they don’t have to loiter 25 minutes at a terminal collecting dust and depreciating. If they come every 5 minutes, they’re not going to loiter 25 minutes anyway, and the difference between a 5-minute turnaround and a 7-minute turnaround is not really relevant.

The design principles are then mostly about throughput, again. The most important thing is to build independent trunk lines for trains to serve city center. Even in a huge city, the finances of building a purely greenfield subway deep into suburbia are poor; Tokyo has done it with the Tsukuba Express but it’s mostly above-ground, and for the most part regional lines there and elsewhere come from taking existing suburban lines and linking them with city center tunnels.

Tokyo’s insistence on making these city center tunnels also form a coherent metro network is important. Only one non-Tokyo example is worth mentioning to add to all of this: this is Berlin, which is not a megacity but has three independent S-Bahn trunk lines. Berlin, unlike London and Paris, painstakingly made sure the S-Bahn lines would have transfers with the U-Bahn; its network has only one U-Bahn/S-Bahn missed connection, which is better than the situation in Tokyo, Paris, or (with Thameslink and Crossrail) London.

The role of development

All first-world megacities, and I believe also all megacities elsewhere, have high housing demand by domestic standards. All are very wealthy by domestic standards except Los Angeles, and Los Angeles is still incredibly expensive, it just doesn’t have the high wages to compensate that London and New York and Paris have. In such an environment, there’s no need to try to be clever with steering development to transit-oriented sites. Anywhere development is legal, developers will build, and the public transport system has a role to play in opening more land for more intense development through fast trips to the center.

A laissez-faire approach to zoning is useful in such an environment. This contrasts with smaller cities’ reliance on finger plans, like the original one in Copenhagen or the growing one in and around Berlin. No limits on development anywhere are required. The state’s planning role remains strong through transportation planning, and the suburbs may well form natural finger plans if developers are permitted to replace single-family houses with apartment buildings anywhere, since the highest-value land is near train stations. But state planning of where housing goes is counterproductive – high transit ridership comes from the impossibility of serving a large central business district by cars, and the risk of politicization and policy capture by homeowners is too great.

The advantage of this approach is also that because in a high-demand city public transport can to some extent shape and not just serve development, it’s okay to build lines that are good from the perspective of network coherence, even if the areas they serve are a bit light. This principle does not extend indefinitely – subway and regional rail lines should still go where people are – but for example building key transfer points in near-center neighborhoods that are not in high demand is fine, because demand will follow, as is building lines whose main purpose is to close some gap in the network.

Construction costs

The larger the city, the more important cost control is. This may sound counterintuitive, since larger cities have more demand – only in Manhattan could a $1.7 billion/km extension like Second Avenue Subway pencil out – but larger cities also have a bigger risk of cost blowouts. Already Tokyo has stopped building new rapid transit in the core despite very high crowding levels on the existing network, and London builds next to nothing as well. New York’s poor cost control led Philip Plotch to entitle his book about Second Avenue Subway The Last Subway. Even Paris builds mostly in the suburbs. Extensive city center and near-center construction continues in Seoul, in the context of very low construction costs.

The flip side is that a New York (or even London) that can build subways at the cost of Paris, let alone Seoul, is one that can rapidly solve all of its transport problems. My Assume Nordic Costs map fixates on a region of the world with small cities, but the construction costs in South Korea are if anything lower than in the Nordic countries. And even that map, given free reins for developers, is underbuilt – some lines would look ridiculous at current costs and zoning but reasonable given low costs and liberal zoning, for example something meandering through currently industrial parts of New Jersey.

Small cities designed their public transportation philosophy around scarcity: Switzerland really can’t just draw crayon and build it, because housing and transport demand there are finite and limited. Cities like New York and London, in contrast, should think in terms of abundance of infrastructure and housing, provided their regulations are set up in a way that permits the state to build infrastructure at low costs and private homebuilders to redevelop large swaths as they become easily accessible to city center.

More on Suburban Circles

In the last post, I criticized the idea of large-radius suburban circle, using the example of the Berlin Outer Ring, at radius 10-26 km from city center. In comments, Andrew in Ezo brought up a very good point, namely that Tokyo has a ring at that radius in the Musashino Line, and ridership there is healthy enough to fill a train every 10 minutes off-peak. Of course, the Musashino Line’s intersections with the main JR East lines, like Nishi-Kokubunji and Minami-Urawa, have the ridership of a city center station in Germany rather than that of a station 25 km out. So to discuss this further, let’s drop midsize cities like Berlin and look at an actually large city: New York. Consider the following possible circle in New York, at radius 20-25 km:

See full-size version here (warning: 55 MB).

Most of the radial extensions I’ve already discussed in previous posts – for example, here. Here these extensions go somewhat further in order to meet the ring, including at Newark Airport, on Staten Island, in Bay Ridge, at Floyd Bennett Park, in Canarsie, at Starrett City, near the Queens/Nassau County line, and in Yonkers.

The ring is 151 km, of which around 87 km would be above ground, mostly replacing highways like the Belt Parkway to reduce costs. Of note, this cannot be done adjacent to an extant highway – the fast car traffic deters nearby development, making transit-oriented development impossible. So key road links around the region have to go, which is fine, since people should be transitioning from driving to taking trains. With some additional elevated construction including through City Island, across the Long Island Sound, and in low-density parts of North Jersey where demolishing houses even at $1 million per unit is cheaper than tunneling, construction costs could be reduced further. But it’s still a $20-25 billion project at average world costs, maybe $15 billion at Nordic or Korean or Southern European or Turkish costs.

The only way to pay off the costs of such a line, not to mention to fill enough trains to support frequency that can take untimed transfers (at worst a train every 10 minutes), is to have very high ridership, on the order of 400,000-500,000 per day. This is for a line that misses Manhattan and all of the big secondary job centers, like Downtown Brooklyn and Long Island City. Is this plausible?

The answer is not an obvious no. Sufficiently aggressive TOD could plausibly create ridership. But it’s still questionable. There are really a few different forces pulling such a line in different directions:

  • Using existing rights-of-way to reduce costs, hence the use of the Belt Parkway and not the denser development around Avenue U or even Flatlands.
  • Serving secondary nodes like JFK, Coney Island, EWR, and Yonkers. Potentially it would be plausible to veer inward in New Jersey in order to hit Downtown Newark, at the cost of a few extra kilometers of tunnel, making the line radial from Newark’s perspective, whereas the line as depicted above is circumferential from Newark’s perspective since it goes around city center.
  • The need to connect to radial subway and commuter rail lines, which means serving stations, opening plausible infill stations, and extending some lines toward the ring.

There are different ways to resolve this tension; the line I depicted is not the only one. For example, a higher-cost, higher-ridership version could veer inward in the Bronx and Queens, aiming to connect to Flushing and Jamaica and then replace the AirTrain JFK, leading to a ring of radius closer to 16 km than to 20-25.

I only bring this up to point out how many things have to work if you want such a ring to work out. Keeping costs to even semi-reasonable levels requires demolishing highways and engaging in aggressive TOD, which is only possible in an environment of total political victory over NIMBY and pro-car interests (note: these two are not the same!).

This is not the history of the Musashino Line. The Musashino Line originates in a freight bypass around the built-up area of Tokyo, which eventually turned into a circumferential passenger line. This is why it connects to the radial lines near but not at the busiest regional stations – at Nishi-Kokubunji and not Kokubunji, at Minami-Urawa and not Urawa, at Shin-Matsudo and not Matsudo or Kashiwa.

But even when the line is new, there are always compromises on right-of-way. Uncompromised right-of-ways are 100% possible, but not at 25 km radius, because the cost is too high to always go to the most important secondary centers. They happen when the radius is smaller, like Paris’s 8-10 km for M15, because then ridership can be high enough (M15 projects nearly a million riders a day). Farther away, ridership drops and costs rise because the line gets longer faster than per-km costs drop, so compromises are inevitable.

I am not proposing the ring above as a definitive crayon. I’m just mentioning it as something that highlights the difficulties of circumferential public transportation in the suburbs. Even as it is, the strongest segment of the ring is most likely the one in the city taking over the Belt Parkway, which could replace busy buses like the B15, B1, B3, B6, and B82. The suburban segments are weaker – there isn’t that much commuting across the Hudson that far north, and building up such commuting requires heavy commercial TOD in Yonkers, Mount Vernon, and New Rochelle.

The Limit of Circles in the Suburbs

In dense urban cores, it’s valuable to run circular rail lines. They connect dense near-center neighborhoods to one another without going through the more congested center, and help make transferring between parallel lines more efficient, again through avoiding central business district congestion. Some of the largest cities in the world even support multiple circles, line Lines 2 and 10 in Beijing, or the various overlapping circles of Moscow, Tokyo, and soon Paris. However, this system of radial lines through the center and circular lines around the center cannot go on forever. There is a limit to how far out one can build circles, which is much sharper than the limit of how far radial lines can go. Lower-density suburbs can have radial lines connecting them to city center or to near-center nodes of activity, but circumferential lines are likely to be weak.

For a concrete example, take Berlin. It has the Ring through fairly dense neighborhoods, supporting 5-minute frequency on the S-Bahn during most of the day. But it also has the Outer Ring, built in the 1950s through East Berlin and the Brandenburg suburbs to surround West Berlin and permit the construction of the Wall; today it runs regional trains, and one segment through East Berlin runs the S75 every 10 minutes, but there is no train making the entire orbit, just trains using short segments to position themselves to a better radial entry into the center of Berlin. It looks frustrating – there is circular infrastructure, why not use it? But there’s a solid reason not to run it as a true circle.

See map below:

A schematic of service patterns can be seen here.

The line’s origin as a bypass means it doesn’t serve any of the nodes near its radius, like Potsdam (too built-up), Spandau (in West Berlin), or Märkisches Viertel (also in West Berlin). The only node it does pass through is the soon-to-close Schönefeld airport, which only became important well into the Cold War; moreover, a branch parallel to the line to the southeast serves the soon-to-open Berlin-Brandenburg Airport, with plans to run many different kinds of regional services entering Berlin from both the Stadtbahn and the North-South Main Line. So a circular service would, by itself, just connect various outlying areas like Marzahn, Hennigsdorf, and Falkensee to the airport. By itself, this doesn’t support very high frequency.

Now, what the line could do is work as a network together with radial lines, connecting to them to facilitate travel not passing through the center of Berlin. However, there is not much point in transfers unless they are either high-frequency or timed. High-frequency transfers are out – the radial lines that penetrate the Outer Circle run 2-3 trains per hour. This forces the transfers to be timed.

Timed connections on lines that intersect crosswise rather than parallel with cross-platform transfers are completely possible. The trains can’t be too long, but that’s fine, a 4-car train with stair and elevator connections could have 2-3 minute transfer windows and still exchange passengers in all directions. It’s worth establishing at sufficiently important stations where a cross-platform transfer is not possible; as a four-way transfer, it’s not even that much more involved than a cross-platform transfer with timed wrong-direction transfers like Wittenbergplatz between U2 and U1/3. However, this is for one station.

All of this goes out the window when a circle intersects 12 different radial lines. Such a scheme can only work if all of the transfers are timed, or at least a large majority of them. Otherwise, people might as well take the train through the center and connect at Berlin Hauptbahnhof, or even stay on the same train if it runs through like RE 1 or RE 3.

In theory, you can time a short succession of transfers on the same line. All it really takes is to make sure that the circular line takes a half-integer multiple of the takt interval between every pair of transfer points, allowing both-direction transfers everywhere. On a few stretches of the line, it’s even plausible, with a 20-minute takt – the line would be fast because it’s so far out and has to few stops, so 7-10 km in 8 minutes (10 minus 2 for the transfer window) is not outside the realm of possibility.

Except that some segments between transfer points are still bad, like between the two just west of Spandau, or on both sides of the crossing with S5 and RE 1 in Lichtenberg. And even if they weren’t, this runs into the problem that trains are not infinitely punctual. Having 12 knots between a circular line and radials around Berlin, or even just 10 if weak ones are dropped, means that suburban Berlin would have more knots every 20 minutes than Switzerland has today every half hour (8), and not too many fewer than Switzerland is planned to have every half hour in the 2030s. The required schedule discipline is intense, especially in a big city defined by crowded rush hour trains.

This has implications elsewhere. Paris has its Grande Ceinture, which is tempting for a regional rail ring, but the frequency at which it can support a full RER line is not high; instead, the region is breaking the line into segments, to be turned over into tram-trains, with some segments diverging from the mainline to serve nodes near but not on the line.

In general, what this means is that if you’re not connecting to a major city center, there’s only so much service you can run. If you’re within the densely built-up area, as the Ring is or as the various orbitals Paris has (M2/M6, T3) or plans (M15), then it’s fine – untimed transfers are fine when trains come every 5 minutes, and overlapping one-seat rides like Prenzlauer Berg-Neukölln and Ostkreuz-Tempelhof and so on can help fill the train as well. But once frequency drops below about a train every 10 minutes, untimed transfers no longer work, which means that services that rely on connections only work if the connections are at a handful of key points, not at 12 different radii around the city.