Category: Good Transit

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.

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.

Stadtbahn Systems

I made an off-hand remark about subway-surface systems, called Stadtbahn in German (as is, confusingly, the fully grade-separated east-west Berlin S-Bahn line), regarding a small three-line single-tail network that Brooklyn could build. I also talked about it in a little more detail last year. I want to go more deeply into this now. It’s a public transportation typology that’s almost nonexistent outside Germany and Belgium; Tel Aviv is building one line, and the US has three but two of those are from more than 100 years ago. But there are interesting examples of good places to use this technology elsewhere, especially elsewhere in Europe.

What is the Stadtbahn?

The Stadtbahn (“city rail”), or the subway-surface line in US usage, is an urban line running light rail vehicles, with grade separation in city center and street running outside city center. All examples I know of are in fact underground in city center, but elevated lines or lines running in private rights-of-way could qualify too, and in Cologne, there’s a semi-example over a bridge dropping to the surface at both ends.

It’s best illustrated as a 2*2 grid:

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

The terms fast and slow are relative to general traffic, so a mixed-traffic bus in a low-density city that averages 30 km/h is slow whereas the Paris Métro, which averages 25 km/h, is fast; the speed in km/h may be higher on the bus, but the speed in destinations accessed per hour is incomparably higher on the Métro.

The tram-train is confusingly also called Stadtbahn in Germany, for example in Karlsruhe; this is nearly every light rail built in North America. It is not the topic of this post.

What is the purpose of the Stadtbahn?

Historically, Stadtbahn systems evolved out of pure surface tramways. City center congestion made the streetcars too slow, so transit agencies put the most congested segments underground. This goes back to Boston in 1897 with the Tremont Street Subway and Philadelphia in 1906 with the Subway-Surface Lines. The contrast both in that era and in the era of Stadtbahn construction in Germany from the 1960s to the 80s is with pure subways, which are faster but cost more because the entire route must be underground.

Stadtbahns always employ surface branching. This is for two reasons. First, there’s more capacity underground than on the surface, so the higher-capacity rapid transit segment branches to multiple lower-capacity tramways to permit high throughput. And second, there’s generally less demand on the outer segments than in the center – lines with very strong demand all the way tend to turn into full subways.

This is therefore especially useful for cities that are not huge. In a city the size of Cologne or Stuttgart or Hanover, there isn’t and will never be demand for a rapid transit system with good citywide coverage. Instead, there is something like a sector principle. For example, in Cologne, the Deutz side of the city, on the right bank of the Rhine, has service to city center on the S-Bahn, on tramway lines over the Deutzer Bridge branching on the surface, and on tramway lines over the Mülheimer and Severin Bridges feeding into the north-south ring Stadtbahn. Smaller cities have simpler systems – Hanover for has three underground trunk lines meeting at one central station, and Dortmund has three meeting in a Soviet triangle. This maintains good coverage even without the budget for many rapid transit lines.

Where are Stadtbahns appropriate?

Cities should consider this technology in the following cases:

  • The city should not be too big. Tel Aviv is too big for this, and people in Israel are starting to recognize this fact and, in addition to the under-construction three-line Stadtbahn system are proposing a larger-scale three-line fully grade-separated metro system. If the city is big enough, then a full metro system is justified.
  • There should be a definitive city center for substantial traffic to funnel to. The purpose of the Stadtbahn is to have comparable throughput to that of a metro, albeit with shorter trains.
  • There should be wide swaths of sectors of the city where having multiple parallel lines is valuable. This, for example, is the case in cities that are not exceptionally dense and cannot expect transit-oriented development to completely saturate one metro corridor.
  • The street network should not be too gridded, because then the sector-based branching is more awkward, and the combination of rapid transit to city center and a surface transit grid can be powerful, as in Toronto.
  • There should be too much city center congestion for a pure surface system to work, for example if most streets are very narrow and traffic funnels to the few streets that can use

These circumstances are all common to German urbanism: city centers here are strong, but residential density peaks at 15,000/km^2 or thereabouts in near-center neighborhoods and drops to 3,000-6,000/km^2 farther out. Moreover, Germany lacks huge cities, and of the largest four urban cores – Berlin, Hamburg, Munich, Frankfurt – three have full rapid transit systems. Finally, grids are absent here except at very small scale, as in Mannheim.

However, these are not unique features to Germany. They’re common around Europe. European cities are not very big, and the only ones that can genuinely fill any subway line with transit-oriented development are a handful of very big, very rich ones like London and Paris. Even Stockholm and Munich have to be parsimonious; they have have full metro systems with branching.

The French way of building rapid transit does not employ the Stadtbahn, and perhaps it should. In a city the size of Bordeaux or Nice, putting a tramway underground in city center and then constructing new branches to expand access would improve coverage a lot.

This is likely also the case in Italian cities below the size class of Milan or Rome. Many of these cities are centered around Renaissance cores with very narrow streets, which are nonetheless auto-centric with impossibly narrow sidewalks, Italy having nearly the highest car ownership in Europe. Finding one to three good corridors for a subway and then constructing tramways funneling into them would do a lot to speed up public transit in those cities. Bologna, for example, is planning a pure surface tramway, but grade-separated construction in the historic center would permit trams to have decent coverage there without having to slow down to walking speed.

Are there good examples outside Europe?

Yes! From my original post from 2016, here is one proposal for New York:

The B41 could be a tramway going between City Hall and Kings Plaza, using two dedicated lanes of the Brooklyn Bridge. In that case, the line would effectively act as subway-surface, or more accurately elevated-surface: a surface segment in Brooklyn, a grade-separated segment between Manhattan and Brooklyn. Subway-surface lines should branch, as all current examples do (e.g. Boston Green Line, Muni Metro, Frankfurt U-Bahn), because the subway component has much higher capacity than the surface components. This suggests one or two additional routes in Brooklyn, which do not have strong buses, but may turn into strong tramways because of the fast connection across the river to Manhattan. The first is toward Red Hook, which is not served by the subway and cut off from the rest of the city by the Gowanus Expressway. Unfortunately, there is no really strong corridor for it – the streets are not very wide, and the best for intermediate ridership in Cobble Hill and Carroll Gardens require additional twists to get into the core of Red Hook. Court Street might be the best compromise, but is annoyingly a block away from the F/G trains, almost but not quite meeting for a transfer. The second possible route is along Flushing Avenue toward the Navy Yard; it’s not a strong bus by itself, but the possibility of direct service to Manhattan, if a Flatbush tramway preexists, may justify it.

Note that this proposal is opportunistic: Brooklyn Bridge just happens to be there and point in the right direction for at least one strong surface route in Brooklyn, and conversely would connect too awkwardly to the subway. In a city the size of New York, Stadtbahn lines must be opportunistic – if the region intentionally builds new river crossings then they must carry the highest-capacity mode of transportation, which is rapid transit, not a light rail variant.

American cities smaller than New York are often very big by European standards, but also very decentralized. This hurts the Stadtbahn as a mode – it really only works for a monocentric city, because if there are multiple centers, then all but the primary one get slow transit. The Rhine-Ruhr notably uses the S-Bahn, which is rapid transit, to connect its various cities, and only run Stadtbahn service internally to each center, like Cologne or Dortmund.

There are a number of places in the United States where burying a light rail line in city center is advisable, but this is for the most part conversion of a tram-train to rapid transit, for examples in Portland and Dallas. The only example that come to mind of a decent Stadtbahn in the US that doesn’t already exist is Pittsburgh, converting the BRT system to rail.

Outside the United States, I get less certain. Canada is bad geography for a Stadtbahn because of its use of grid networks; Ottawa may be good for a Stadtbahn using the Confederation Line tunnel, but that’s probably it. Australia may be better, combining decently strong city centers with very low residential density; transit-oriented development potential there is very high, but it could plausibly come around multiple distinct corridors as well as regional rail stations. Melbourne’s tramways thus may be a candidate for Stadtbahn conversion.

In both East Asia and in the developing world, it’s likely best to just build full metros. East Asian cities are big and have high rates of housing construction (except Hong Kong). I can see a Stadtbahn succeed in Taichung, extending the under-construction Green Line on the surface and building intersecting lines, but that’s probably it. Kaohsiung already has a (very underused) subway, what I think is Daejeon’s best next corridor on top of Line 1 and the planned Line 2 is unusually bad for a Stadtbahn because the streets are too gridded west of the center, Daegu is too gridded as well.

A similar set of drawbacks is also true for the developing world. The urban population of the developing world tends to cluster in huge cities. Moreover, these cities tend to have high residential density but low city center job concentration; the Addis Ababa light rail is bad at serving people’s work trips because so few people work in the center. Finally, the developing world has high rates of increase in urbanization, which make future-proofing systems with higher capacity more valuable.

Some Examples of Falling Costs

Question. Are there any historical examples of construction costs actually falling in a city, rather than just rising slower than elsewhere?

Answer. Yes! Not many, though.

I know of three examples, but the first is fairly irrelevant and is included here for completeness.

Example 1. London’s District line, going by Wikipedia data, cost 3 million pounds, which in today’s money translates to $90 million per kilometer. This was astonishingly expensive, and even today London Underground extensions, as opposed to Crossrail, cost less than that relative to British GDP per capita. The reason for the high cost: the line was built cut-and-cover without any street to go under, so it needed to carve a new right-of-way through Kensington, demolishing houses in an expensive area. No further cut-and-cover lines were built. Costs fell to about $30 million per kilometer with the invention of deep-bore tunneling a generation later; today, bored tunnel costs more than cut-and-cover, but with the technology of the late 19th and early 20th century, this was not the case.

Example 2. Milan built its first two lines very cheaply; in today’s money, M1 cost around $50 million per kilometer. It was built using a method invented specifically for the city’s narrow Renaissance streets called the Milan method or cover-and-cut, allowing vertical construction with retaining walls rather than sloped ones that require more street width. M2 was very cheap as well, but M3’s costs were much higher, I believe around $250 million per km in today’s money, built in the 1980s at the peak of Milanese corruption. Costs fell dramatically after a series of anti-corruption prosecutions that put much of the Italian political elite in prison. The Passante Railway was in today’s money around $140 million per km, not all underground, but it’s regional rail with difficult city center construction under three older lines. The more recent lines, M5 and M4 (in this order), run up to $120-160 million per km.

Example 3. Istanbul began building its subway system with M2, M3, and M4; the first Istanbul Metro line, M1, is light rail and its original section had very little tunneling. It used Italian designs and costs were low, not much more than $100 million per kilometer, but subsequently value engineering has led to slightly lower costs. The city had a learning process in which it reduced station footprints to save money, engaged in more extensive prior engineering before putting out new lines to bid, and generally gained experience in managing a project. Newer lines have cost slightly less, for example around $80 million/km for M5, all underground.

The angle of cleaning up corruption and building up state capacity is probably relevant – probably. Italy and Turkey remain very corrupt and clientelist states. In Turkey, the former mayor of Istanbul openly said he was going to prioritize metro construction in neighborhoods that voted for AKP, and then when the opposition won the city election the state stopped giving it money for new lines; construction goes on because the new mayor went to the European Investment Bank for financing. In Italy, for all the clientelism elsewhere, public-sector engineering is fiercely depoliticized and professionalized nowadays.

I might even speculate, without much knowledge yet (we’re still early in the work in Istanbul and even earlier in Milan), that Southern Europe may have such reputation for corruption that it has mundane mechanisms that professionalize public works. The clientelism in Turkey as far as we can tell extends to macro-level decisions of where to build lines, and evidently Istanbul managed to identify alternative sources of financing to the Erdoganist state.

If I’m right, then these same mechanisms of anti-corruption and public-sector professionalization can also be replicated in other parts of the world with state capacity problems. This cannot possibly be everything – Milan reduced its costs from levels that were not extremely high, and Istanbul was cheap from the start – but it does point in a more optimistic direction.

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.

Integrated Timed Transfer Schedules for Buses

I’ve written a bunch about integrated timed transfer (ITT) scheduling based on Swiss and Dutch principles, developed for intercity and regional trains. Here, for example, is how this schema would work for trains connecting Boston and Worcester. But I’ve also seen interest in how buses can connect to one another, so I feel it’s useful to try to adapt the ITT to this different mode. Two particular places where I’ve seen this interest are a statewide plan for intercity buses in West Virginia, and regional integration around Springfield and the Five Colleges; I’m not going to make specific recommendation for either place, since I don’t know them nearly well enough, but I hope what I write will be helpful there and elsewhere.

The ITT principles for trains

ITT for trains relies on total coordination of all aspects of planning. The centerpiece of this is the triangle of infrastructure, rolling stock, and timetable, all of which must be planned together. Decisions on infrastructure spending should be based on what’s required to run the desired schedule, based on tight turnarounds, maximal utilization rates of equipment, and timed connections.

The even broader principle is to trade state complexity for money. It’s harder to plan everything together – different departments need to talk to one another, planning has to be lean or else the back-and-forth will take too long, regulations may have to be adjusted, government at all levels has to push in the same direction. The reason to do this chore is that it’s far cheaper than the alternative. Organization is cheaper than electronics and concrete at all levels; American households spend around 20% of their income on transportation, mostly cars, whereas households in transit cities like Paris or Berlin or Tokyo spend a fraction of that, even taking into account residual car ownership and operating subsidies to public transit.

On buses, there’s no such thing as electronics…

The Swiss maxim, electronics before concrete, concerns trains exclusively. On buses, no such thing exists. It’s not really possible to get higher-performance buses to make a more aggressive schedule. Acceleration rates depend on passenger safety and comfort and not on the motors (in fact, they’re higher on buses than on trains – rubber tires grip the road better than steel wheels grip rails). The closest analog is that electric buses are lower-maintenance, since the diesel engine is the most failure-prone part on buses as well as trains, but what this leads to, IMC, is not really a strategy for improving timetabling – IMC’s main benefits are less pollution and lower maintenance costs.

…but there is a surplus of organization to be done

All the little things that on trains go in the electronics bucket go in the organization bucket on buses. These include the following operating treatments to improve local bus speeds:

  • Off-board fare collection
  • Stop consolidation to one every 400-500 meters
  • Dedicated lanes in congested areas
  • Signal priority at busy intersections

In addition, bus shelter does not increase actual speed but does increase perceived speed, and should be included in every bus redesign in an area that lacks it.

These are all present in Eric’s and my Brooklyn bus redesign proposal, but that doesn’t make that proposal an ITT plan – for one, it’s based on 6-minute frequencies and untimed transfers, whereas ITT is based on half-hour frequencies (for the most part) and timed transfers. Of note, in a 6-minute context signal priority should be conditional to prevent bunching, but if buses run on a 30-minute or even 15-minute timetable then bunching is less likely, especially if buses have prepayment and some dedicated lanes.

That said, it’s important to talk about all of the above in this context, because a bus ITT belongs in areas where public transport ridership is so low that people view a bus every 15 minutes as an aspirational schedule. In such areas, the politics of giving buses more priority over cars are harder than in a city with low car usage like Paris or New York or Barcelona. There are some positive examples, like Rhode Island’s eventual passage of a bill giving six key bus corridors signal priority, but in Tampa I was told that DOT wouldn’t even let the bus agency bump up frequency unless it found money for repaving the street with concrete lanes.

What about intercity buses?

Prepayment, stop consolidation, and dedicated lanes are important for speeding up local buses. But intercity buses already stop sporadically, and often run on highways. There, speedup opportunities are more limited.

But there may still be some room for signal priority. If the bus only runs every hour or every half hour, then driver resistance may be reduced, since the vast majority of stoplight cycles at an intersection will not interact with a bus, and therefore the effect of the change on car speed will be small.

This is especially important if buses are to run on arterial roads and not on freeways. The significance is that highways are noisy, especially freeways, and do not have the concept of a station – freeways have exits but one takes an exit in a car, not on foot. Therefore, development does not cluster near a freeway, but rather wants to be a few minutes away from it, to avoid the noise and pollution. Arterials are better at this, though even then, it’s common for American big box stores and malls to be somewhat set away from those, requiring bus passengers to walk through parking lots and access roads.

Arterial roads, moreover, often do have stoplights, with punishing cycles optimized for auto throughput and not pedestrian-friendliness. In such cases, it’s crucial to give buses the highest priority: if these are intercity buses rather than coverage service to a suburb where nobody uses transit, they’re especially likely to be full of passengers, and then a bus with 40 passengers must receive 40 times the priority at intersections of a car with just a driver. Moreover, if it is at all possible to design stoplights so that passengers getting off the wrong side of the street, say on the east side for a northbound bus if the main development is west of the arterial, can cross the street safely.

Designing for reliability

The principles Eric and I used for the Brooklyn redesign, as I mentioned, are not ITT, because they assume frequency is so high nobody should ever look at a timetable. But the ITT concept goes in the exact opposite direction: it runs service every 15, 20, 30, or even 60 minutes, on a consistent clockface schedule (“takt”) all day, with arrival times at stations given to 1-minute precision.

Doing this on a bus network is not impossible, but is difficult. In Vancouver, the bus I would take to UBC, the 84, came on a 12-minute takt off-peak, and ranged between on time and 2 minutes late each cycle; I knew exactly when to show up at the station to make the bus. When I asked Jarrett Walker in 2017 why his American bus redesigns assume buses would run roughly every 15 minutes but not on such a precise schedule, he explained how American street networks, broken by freeways, have more variable traffic than Vancouver’s intact grid of many parallel east-west arterials.

So what can be done?

Dedicated lanes in congested areas are actually very useful here – if buses get their own lanes in town centers where traffic is the most variable, then they can make a consistent timetable, on top of just generally running faster. Signal priority has the same effect, especially on arterials as noted in the section above. Moreover, if the point is to make sure the noon timetable also works at 8:30 in the morning and 5:30 in the afternoon, then driver resistance is especially likely to be low. At 8:30 in the morning, drivers see a bus packed with passengers, and their ability to argue that nobody uses those bus lanes is more constrained.

New York as a Six-Minute City

What would it take to improve public transportation in New York so that all or nearly all routes would run at worst even six minutes during midday? Today, frequencies are tailored to individual routes; a bunch of subway lines are a 10-minute city (and the A branches are a 15-minute city), and in Brooklyn, the median midday bus headway is 12 minutes, with wide variations.

The bus origin of six minutes

Six minutes is not an arbitrary number. It comes from Eric’s and my Brooklyn bus redesign; speeding up routes through stop consolidation, dedicated lanes, and off-board fare collection, and pruning and recombining some routes, lets every bus run every six minutes from 6 am to 10 pm all day every day, with higher frequency on those routes that already have it today because they are too busy for just ten buses per hour. We didn’t study the other boroughs as deeply, but a quick doodle suggested the six-minute standard could be met in Manhattan and the Bronx as well, and a Bronx bus grid could even dip into a five-minute city.

Queens is a wildcard and I’m going to disappoint readers by not talking about it. It is clearly possible given the operational treatment we propose to make most of Queens a six-minute city, but at the price of long route spacing in Eastern Queens, and I don’t know what is optimal. It’s a hard question and I’m not going to tackle it unless I’m actually working on a longer-term project to do a Queens bus redesign.

Six minutes on the subway

The subway right now is a 10-minute city. A lettered or numbered route runs every 10 minutes off-peak, sometimes every 12 on Sundays and at night; the busier routes, especially the four that do not share tracks with other routes (1, 6, 7, L), run more frequently, but 10 minutes is the base frequency on large swaths of the network. The A branches in Ozone Park and the Rockaways even run every 15 minutes, but that’s unusual enough – evidently, nowhere else does one letter or number denote a route with its own branches – that it can be excluded.

For comparison, Berlin’s rail network is a 10-minute city, with some outer S-Bahn branches running every 20 minutes. Within the Ring, Berlin is a 5-minute city for the most part, excluding just a two-hour midday dip to 10 minutes on the Ring and 10-minute frequencies on the U1/U3 branches and the practically useless U4 route. Paris makes no effort to run different routes at the same intervals – French rapid transit planning has self-contained lines with their own fleets and schedules, so for example the RER A is on 10-minute off-peak takts and the RER B on 15-minute ones. So frequency there greatly depends on where in the region one lives and on what line. The Métro is a 5-minute city for the most part, as are the intramural RER trunks; intramural buses can be ignored. The suburbs are more or less a 15-minute city.

The reason New York is a 10-minute city on the subway is partly about interlining. The trunks in theory run every 5 minutes or better, but the trains do not come evenly because sometimes trains with different frequencies share the same trunk, and delays propagate easily. Interlining really doesn’t work unless all trains come at the same frequency; this is familiar in German planning, but not in American planning (or French planning, but there’s barely any interlining in Paris).

Putting every subway route on a 10-minute takt, with double service on the four non-interlined services, is possible but would lead to a lot of crowding on the busiest lines. About the worst possible frequency that works for everything is a train every 7.5 minutes; this lets the two A branches run on 15-minute takts, and everything else run on a 7.5-minute takt. But even then, New York has so many missed connections that it’s useful to do better. The six-minute city, matching buses, turns most of Manhattan and inner Brooklyn and Queens into a three-minute city.

Running all trains on the same takt also means timed connections. Trains that run every 5 or 6 minutes can routinely be timetabled to be at predictable places at predictable times, which facilitates local/express transfers on branches, for example in Southern Brooklyn. Even trunk transfers can be timed – 3-minute trains can still run on a timetable, and the most valuable transfers are local/express ones at 96th/Broadway, 125th/St. Nicholas, and 125th/Lex, all far enough north so as to not have the huge tidal crowds of Times Square or Grand Central.

What would it take?

On the buses, just good redesign, as long as the city is willing to exclude Staten Island from the six-minute city. In Queens, some increase in bus service is probably warranted.

On the subway, this requires on the order of 110-120 million revenue train-km a year, which is 1 billion car-km. The current figure is 560 million car-km/year. There is a lot of unnecessary expenditure on the subway, but fixing that requires something a lot deeper than a bus redesign. The cut in operating costs would be to levels that are well within first-world levels, and some of it would just come from better off-peak service making crew scheduling easier, without split shifts or wasted time. But it does require serious changes, especially in maintenance.

Quick Note: Timed Orbital Buses

Outside a city core with very high frequency of transit, say 8 minutes or better, bus and train services must be timetabled to meet each other with short connections as far as possible. Normally, this is done through setting up nodes at major suburban centers where trains and buses can all interchange. For example, see this post from six months ago about the TransitMatters proposal for trains between Boston and Worcester: on the hour every half hour, trains in both directions serve Framingham, which is the center for a small suburban bus system, and the buses should likewise run every half hour and meet with the trains in both directions.

This is a dendritic system, in which there is a clear hierarchy not just of buses and trains, but also of bus stops and train stations. Under the above system, every part of the Framingham area is connected by bus to the Framingham train station, and Framingham is then connected to the rest of Eastern New England via Downtown Boston. This is the easiest way to set up timed rail-bus connections: each individual rail line is planned around takt and symmetry such that the most important nodes can have easy timed bus connections, and then the buses are planned around the distinguished nodes.

However, there’s another way of doing this: a bus can connect two distinct nodes, on two different lines. The map I drew for a New England high- and low-speed rail has an orbital railroad doing this, connecting Providence, Worcester, and Fitchburg. Providence, as the second largest city center in New England, supplies such rail connections, including also a line going east toward Fall River and New Bedford, not depicted on the map as it requires extensive new construction in Downtown Providence, East Providence, and points east. But more commonly, a connection between two smaller nodes than Providence would be by bus.

The orbital bus is not easy to plan. It has to have timed connections at both ends, which imposes operational constraints on two distinct regional rail lines. To constrain planning even further, the bus itself has to work with its own takt – if it runs every half hour, it had better take an integer multiple of 15 minutes minus a short turnaround time to connect the two nodes.

It is also not common for two suburban stations on two distinct lines to lie on the same arterial road, at the correct distance from each other. For example, South Attleboro and Valley Falls are at a decent distance, if on the short side, but the route between them is circuitous and it would be far easier to try to set up a reverse-direction timed transfer at Central Falls for an all-rail route. The ideal distance for a 15-minute route is around 5-6 km; bus speeds in suburbia are fairly high when the buses run in straight lines, and if the density is so high that 5-6 km is too long for 15 minutes, then there’s probably enough density for much higher frequency than every half hour.

The upshot is that connections between two nodes are valuable, especially for people in the middle who then get easy service to two different rail lines, but uncommon. Brockton supplies a few, going west to Stoughton and east to Whitman and Abington. But the route to Stoughton is at 8.5 km a bit too long for 15 minutes – perhaps turning it into a 30-minute route, either with slightly longer connections or with a detour to Westgate (which the buses already take today), would be the most efficient. The routes to Whitman and Abington are 7 km long, which is feasible at the low density in between, but then timetabling the trains to set up knots at both Brockton and Abington/Whitman is not easy; Brockton is an easy node, but then since the Plymouth and Middleborough Lines are branches of the same system, their schedules are intertwined, and if Abington and Whitman are served 15 minutes away from Brockton then schedule constraints elsewhere lengthen turnaround times and require one additional trainset than if they are not nodes and buses can’t have timed connections at both ends.

Planners then have to keep looking for such orbital bus opportunities. There aren’t many, and there are many near-misses, but when they exist, they’re useful at creating an everywhere-to-everywhere network. It is even valuable to plan the trains accordingly provided other constraints are not violated, such as the above issue of the turnaround times on the Old Colony Lines.