Category: Sweden

Density and Rail Transport (Hoisted from Social Media)

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

What is density?

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

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

Density and regional rail

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

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

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

Integrated regional networks

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

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

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

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

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

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

What about low-density places?

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

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

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

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

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

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

No Cafe Cars, Please

European and American intercity train planning takes it as a given that every train must have a car dedicated to cafeteria service. This is not the only way to run trains – the Shinkansen doesn’t have cafe cars. Cafe cars waste capacity that could instead be carrying paying passengers. This is the most important on lines with capacity limitations, like the Northeast Corridor, the West Coast Main Line, the LGV Sud-Est, and the ICE spine from the Rhine-Ruhr up to Frankfurt and Mannheim. Future high-speed train procurement should go the Shinkansen route and fill all cars with seats, to maximize passenger space.

How much space do cafe cars take?

Typically, one car in eight is a cafe. The standard European high-speed train is 200 meters long, and then two can couple to form a 400-meter train, with two cafes since the two 200-meter units are separate and passengers can’t walk between them. In France, the cars are shorter than 25 meters, but a TGV has two locomotives and eight coaches in between, so again one eighth of the train’s potential passenger space does not carry passengers but rather a support service. Occasionally, the formula is changed: the ICE4 in Germany is a single 12-car, 300-meter unit, so 1/12 of the train is a cafe, and in the other direction, the Acela has six coaches one of which is a cafe.

A 16-car Shinkansen carries 1,323 passengers; standard class has 5-abreast seating, but even with 4-abreast seating, it would be 1,098. The same length of a bilevel TGV is 1,016, and a single-level TGV is 754. The reasons include the Shinkansen’s EMU configuration compared with the TGV’s use of locomotives, the lack of a cafe car in Japan, somewhat greater efficiency measured in seat rows per car for a fixed train pitch, and a smaller share of the cars used for first class. An intermediate form is the Velaro, which is an EMU but has a cafe and three first-class cars in eight rather than the Shinkansen’s three in 16; the Eurostar version has 902 seats over 16 cars, and the domestic version 920.

The importance of the first- vs. second-class split is that removing the cafe from a European high-speed train means increasing seated capacity by more than just one seventh. The bistro car is an intermediate car rather than an end car with streamlining and a driver’s cab, and if it had seats they’d be second- and not first-class. A German Velaro with the bistro replaced by a second-class car would have around 1,050 seats in 16 cars, almost even with a 4-abreast Shinkansen even with four end cars rather than two and with twice as many first-class cars.

How valuable are cafes to passengers?

The tradeoff is that passengers prefer having a food option on the train. But this preference is not absolute. It’s hard to find a real-world example. The only comparison I am aware of is on Amtrak between the Regional (which has a cafe) and the Keystone (which doesn’t), and Regional fares are higher on the shared New York-Philadelphia segment but those are priced to conserve scarce capacity for profitable New York-Washington passengers, and at any rate the shared segment is about 1:25, and perhaps this matters more on longer trips.

Thankfully, the Gröna Tåget project in Sweden studied passenger preferences in more detail in order to decide how Sweden’s train of the future should look. It recommends using more modern seats to improve comfort, making the seats thinner as airlines do in order to achieve the same legroom even with reduced pitch, and a number of other changes. The question of cafes in the study is presented as unclear, on PDF-p. 32:

Food and RefreshmentsWillingness to Pay
Coffee machine (relative to no service at all)3-6%
Free coffee and tea in each car6%
Food and drink trolley11%
Cafeteria14%
Restaurant with hot food17%

Put another way, the extra passenger willingness to pay for a cafeteria compared with nothing, 14%, is approximately equal to the increase in capacity on a Velaro coming from getting rid of the bistro and replacing it with a second-class car. The extra over a Shinkansen-style trolley is 3%. Of course, demand curves slope down, so the gain in revenue from increasing passenger capacity by 14% is less than 14%, but fares are usually held down to a maximum regulatory level and where lines are near capacity the increase in revenue is linear.

Station food

Instead of a bistro car, railroads should provide passengers with food options at train stations. In Japan this is the ekiben, but analogs exist at major train stations in Europe and the United States. Penn Station has a lot of decent food options, and even if I have to shell out $10 for a pastrami sandwich, I don’t think it’s more expensive than a Tokyo ekiben, and at any rate Amtrak already shorts me $90 to travel to Boston. The same is true if I travel out of Paris or Berlin.

Even better, if the station is well-designed and placed in a central area of the city, then passengers can get from the street to the platform very quickly. At Gare de l’Est, it takes maybe two minutes, including time taken to print the ticket. This means that there is an even broader array of possible food options by buying on the street, as I would when traveling out of Paris. In that case, prices and quality approach what one gets on an ordinary street corner, without the premium charged to travelers when they are a captive market. The options are then far better than what any bistro car could produce, without taking any capacity away from the train at all.

Building Depth and Window Space

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

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

The issue of building depth

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

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

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

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

However…

Euroblocks are complicated

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

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

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

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

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

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

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

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

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

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

What does this mean?

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

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

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

The Greta Effect

Bloomberg is reporting that Germany and Sweden are seeing a trend of reduced domestic air travel and greater rail usage. In Germany, intercontinental air traffic is up 2% year-over-year and international European traffic is down 2%, but domestic traffic has crashed in the last few months and is down 12% now. In Sweden, domestic air traffic is down 11%.

The Greta effect

Greta Thunberg famously crossed the Atlantic by sailboat to avoid personally contributing to greenhouse gas emissions. But she’s fairly practical about alternatives and said right out that she travels in such conditions to highlight how difficult complete decarbonization is. She is also very insistent on the fact that while changes in behavior are nice, collective political action is still needed.

Moreover, the young (as in, younger than me) Greens I meet in Germany are themselves practical as well. The more committed might take a train to France or Italy, but there’s not much interest in back-to-the-land 1960s communes, degrowth, or political revolution in the sense of the socialists and anarchists. Nor have I seen anti-nuclear sentiments recently – the one anti-nuclear sign I saw at the September 20th climate march, which had 100,000 people in attendance, was held by a pensioner and someone who looked 40, whereas the median age at the rally looked like 20.

It’s relatively easy to change travel behavior to avoid domestic flying in Germany as well as Sweden. Domestic rail travel pain in Germany means hourly Hamburg-Munich and Berlin-Stuttgart trains take 5:40 each. International rail travel pain means Berlin-Paris trains take 8:11 with a short transfer that I don’t trust DB or SNCF to meet. Domestic trains only get this long if many transfers are needed, in which case the main competition to the train is the car rather than the airplane, or if one needs to travel between Umeå (population 123,000) and central or southern Sweden. It’s thus likely that the shift in travel pattern reflects a change in consumer desires to avoid polluting – other explanations, such as the grounding of the 737 MAX, would equally affect domestic and European air travel.

Upcoming carbon taxation

Germany has been planning climate legislation for years, but the September 20th protest created a lot of pressure on the government to enact an aggressive package. A carbon tax will begin at €25/t-CO2 in 2021 and rise to €55/t by 2025, where the original plan was to only go up to €35/t. Sweden has had a carbon tax going back to 1991; starting in 2014, the Löfven cabinet has hiked the tax on industry to match the tax on transportation, both currently at €114/t. The effects on the German economy are to be seen, but in Sweden, economic growth has been healthy throughout this period, ahead of any not-newly-industrialized developed country save Australia (although the differences near the top are small).

In addition to the German carbon tax package, the EU is planning to levy a carbon tax on jet fuel for internal flights; so far, international emissions, including international aviation and shipping, are not subject to carbon tax. A leaked report suggests the EU is considering a tax of €330 per 1,000 liters of jet fuel, which corresponds to a hefty €130/t-CO2, the high figure coming from the fact that a ton of CO2 emitted at high altitude causes more global warming than one emitted at ground level. A very fuel-efficient plane like the A320neo consumes 2.25 liters per 100 seat-km on a 1,200 km flight, raising fares on a full flight by €9.06, which is not a game changer but is noticeable at low-cost carrier rates.

Planning for busier trains

The upshot is that demand for flights in Europe is likely to go down, shifting toward rail. The article linked above about the Greta effect says that DB expects its intercity rail traffic to double to 260 million passengers a year by 2040. The article makes no mention of which further investments in intercity rail DB is assuming, but a virtuous cycle is likely: higher ridership justifies more investment, and faster and more convenient trains attract higher ridership.

Of note, the weakness of international rail in Europe points to international connections as an investment priority. In Sweden, trains from Stockholm are fast toward Gothenburg and Malmö, averaging almost 140 km/h, and there are unfunded plans for high-speed rail connecting the three largest cities. However, Stockholm-Oslo trains are quite slow (about 6 hours for what looks like 500 km), even though Oslo is bigger than Gothenburg and Malmö and there are extensive economic and cultural connections between the Nordic countries. The Greens have called for Stockholm-Oslo high-speed rail, and the government should work with Norway on establishing such a line.

In Germany, the situation is different. London and Paris are vast cities, and Paris is within reasonable high-speed rail distance of most of Germany, with good connections on the French side and poor ones on the German one. Trains between Paris and Frankfurt take about 3:48, of which 1:47 is between Paris and Saarbrücken on the German side of the border, a distance of 380 km, and then 2:00 is between Saarbrücken and Frankfurt, a distance of about 200 km by rail and 160 by air. In Belgium, the existing high-speed line east of Brussels is compromised to the point of being slower between Brussels and Liège or Aachen than legacy lines like Stockholm-Gothenburg or London-Manchester.

The reason the map of the high-speed rail I think Germany should build is heavy on international connections is mostly that Europe is gradually building thicker international economic and social connections. However, a future with more expensive air travel and a consumer taste for greener ways of travel does not change the basic picture, and makes it more urgent.

(Map legend: blue is existing or under-construction lines, red is lines that are either in planning or not even in planning but should be built.)

Speed and capacity

DB’s forecast for 260 million annual rail travelers argues in favor of building more capacity. However, in no way does this conflict with building a dedicated high-speed rail network for Germany. On the contrary, the bypasses providing relief to congested lines are already planned to be high-speed: this was the case for the Tokaido Shinkansen and LGV Sud-Est decades ago, and this is now the case for HS2 and the planned Frankfurt-Mannheim express connection.

A largely dedicated network for high-speed passenger rail, with freight using the legacy lines, improves intercity rail reliability, allowing average speeds to rise to be closer to their theoretical technical maximums. Average speeds of 250 km/h on a few lines are plausible, as on Paris-Strasbourg or Madrid-Barcelona. Moreover, through-tunnels enabling intercity trains to run through Frankfurt and possibly Munich without reversing direction facilitate planning high-speed rail as a separate system. Timed connections with regional trains remain important, but critical trunks like Frankfurt-Cologne and Berlin-Hanover can run very frequently.

The schedule I tried writing for the above map in which domestic city pairs mostly run every half hour all day, interlining on a few trunks, assumes ridership of about 250 million. This is not the same as DB’s forecast of 260 million: this counts only high-speed rail riders, and assumes the average trip is 350 km long. To get from DB’s forecast to 87.5 billion p-km per year requires the virtuous cycle of higher ridership and more investment to work over time, but this is plausible given high levels of investment.

Green convenience

When Greta talks about systemic solutions, she understands that it’s important to make it easier to live a comfortable life without greenhouse gas emissions and harder to live one with high emissions. There are many aspects to green convenience: carbon-free electricity (largely achieved in Sweden but not in Germany), pedestrian- and bike-friendly streets, urban and periurban public transport, intercity and freight rail, passive solar design, urban density, carbon-free industrial power generation.

In every case, it’s important to seize upon any social, economic, or political trend that facilitates the green option. If people want to live in big central cities, then governments should make it easy to build housing there so that more people can enjoy the low-carbon wealth of Munich or Stockholm rather than live in cheap declining rural areas and drive. If people support solar power, then governments should leverage its political popularity and subsidize it to decarbonize electricity.

In the case of intercity transportation, a shift in taste toward intercity rail is a cause for celebration. Europe is full of intercity trunk lines ranging from ones that scream “build me now” no matter what (HS2, completing Berlin-Munich, etc.) to speculative ones. Any positive shift toward rail justifies adding ever more marginal intercity rail lines to the network. Perhaps if the network I mapped was justified before the Greta effect, after the Greta effect the most marginal parts of the network (like Stuttgart-Würzburg) are on more solid footing, while unmapped marginal lines like Munich-Prague or even Bremen-Oldenburg-Groningen become plausible.

But celebration does not mean idleness. Climate change is a systemic issue. The state must plan ahead, using the shift toward rail to plan further investments now so that they open in the 2020s and early 30s. This way, the rail network will meet near- and medium-term growth in demand, while stimulating long-term growth, to be satisfied through future investment, paid by taxes on the richer Germany of the 2030s. Good transit activists should take a page from Greta’s refusal to treat good news as grounds for letting up, and demand intensive investment in Europe’s rail network to ensure that green travel will be more convenient, featuring higher speeds rather than more sitting on luggage in the corridors of full trains.

How Come Carbon Taxes are Good for the Economy?

Two of the cities I have lived in are in areas with a carbon tax regime: Vancouver and Stockholm. British Columbia implemented a carbon tax starting in 2008, at a level reaching C$30 per metric ton of CO2, under the right-wing BC Liberals, who favored the carbon tax as a market-friendlier approach than the left-wing NDP’s proposal for cap-and-trade. The tax was revenue-neutral, offsetting other taxes, and is seen as a success; the NDP has since won power and announced a hike in the tax to C$50/t by 2021.

Sweden’s carbon tax is higher and older. It was implemented by the Social Democrats in 1991, at a rate of 24/t for home use, such as fuel, and 6/t for industrial use; it has been subsequently hiked multiple times, reaching 88/t for home use by 2004, and Löfven’s coalition of Social Democrats and Greens has increased it to 114/t for both home and industrial use. Our World in Data cites it as a success too, linking it to high levels of political trust and low corruption levels in Sweden as well as in other European countries with carbon taxes, such as Switzerland.

The question of interest is, how come these carbon taxes are good not just for reducing greenhouse gas emissions, but also for the economy? British Columbia’s economy has grown somewhat faster than that of the rest of Canada. Sweden has had high economic growth since the 1990s as well – see for example World Bank data from 1990 to 2018, in which Sweden’s growth in GDP per capita only behind that of Norway and the Netherlands, both by very small margins. What gives? How come this is apparently good for raw economic growth, when it’s supposed to be an economic distortion that reduces living standards if one ignores long-term environmental benefits?

Negative carbon taxes

There is an array of policies that act as negative carbon taxes – that is, taxes on green activity, or subsidies to polluting activity. The construction of highways is one example – the negative effects of cars include not just climate change but also local air pollution, noise, and car accidents. There are various policies counteracting these effects, such as fuel taxes and mandatory insurance, but they are not enough. For example, in British Columbia the minimum insurance requirement is $200,000 in personal injury plus $300,000 in medical expenses and smaller sums for related torts like funeral costs, but the insurance value of human life is measured in the millions.

To the extent non-carbon taxes on cars are too low, the addition of a carbon tax should move the tax level closer to the true level of the negative externality even ignoring long-term climate change. Carbon taxes should not by themselves improve economic growth on a 30-year horizon, let alone a 10-year one, but lower levels of air pollution, fewer car crashes, and less traffic congestion would.

Another aspect is development. Various zoning laws, such as single-family residential zones in much of Vancouver and restrictions on high-rises in Central Stockholm, encourage people to live and work in lower-density areas. This is simultaneously a negative carbon tax of a sort and a drag on economic productivity. A carbon tax is no substitute for reforms making it easier to add housing – and thankfully, both Stockholm and Vancouver already have fast housing construction, unlike (say) New York – but it does help countermand the subsidies to suburbanization implicit in restrictive zoning.

Climate science vs. arbitrary rule

The economic reasoning behind why special fees on various activities are inferior to broad taxes on income, property, and consumption has to do with incentives and rule of law. Taxing a specific activity incentivizes people and corporations to find creative ways to shift apparent activity elsewhere, creating economic distortions. It also sends everyone a message, “spend more money on lobbying politicians to keep your sector’s taxes lower than those of other sectors.” Broad-based taxes don’t do that, first because the only way to avoid an income tax is to be poorer, and second because there are fewer moving parts to an income or sales tax.

However, carbon taxes are not your run-of-the-mill tax on an activity some politician does not like. Yes, there is a definitive political movement calling for restraining greenhouse gas emissions, but the reasoning behind it is telegraphed years and even decades in advance, and is based on a scientific consensus. Lobbyists can try to fight for exemptions, as they can from income taxes, but the tax itself is based on a process that is transparent to informed economic actors.

In green democracy as in social democracy, the role of the state is not to side with the interest groups that voted for the party in power, unlike in populism. Social democracy holds that the state has an expansive role to play in the economy, but this role is not based on arbitrary exceptions but rather on budgetary and regulatory priorities that have been largely stable for generations: income compression, labor unions, health care, education, child care, infrastructure, housing. It’s not a coincidence that the part of the world with the strongest social-democratic institutions, the Nordic countries, also has more or less the lowest corruption levels.

Green democracy has a different set of priorities from social democracy, but they too are well-known, especially when it comes to the transition away from greenhouse gases. There’s a lot of lobbying concerning specific spending priorities, but the point of a carbon tax is that it adjudicates how to prioritize different aspects of the transition apolitically.

Carbon taxes and good government

The World in Data’s praise of Sweden’s carbon tax regime talks about the necessity for low corruption and high trust levels for a carbon tax to work. But does the causation really run in that direction? What if the causation is different? It’s likely that a carbon tax could politically work in a wide variety of countries, but only in states with high levels of political transparency do politicians prefer it to opaque schemes that reward cronies and favored interest groups.

In other words, once British Columbia enacted its carbon tax the results were positive even without unusually low corruption for a rich country. But for the most part, governments without much transparency or rule of law such as much of the United States do not like the simplicity of a carbon tax. Politicians who call themselves green prefer schemes that either directly subsidize favored groups or at least politically empower them (“Green New Deal”), and that specifically ream difficulties on groups they do not favor (real estate developers, the nuclear industry, etc.).

But that American politicians do not like carbon taxation does not mean carbon taxation could not work in an American context. It does in a Canadian one, without any of the negative economic effects that people who take perverse joy in environmental destruction predicted. The private economy can and does adapt to changes in relative prices, as fuel becomes much more expensive and other products become cheaper to compensate – and judging by the experience of Sweden in particular, even a fairly high tax is compatible with fast economic growth for a mature economy. All it takes is someone willing to spend short-term political capital on the long-term green transition.

Construction Costs in the Nordic Countries

I write a lot about stereotypes in the context of construction costs. Countries with a reputation for corruption, such as Spain, South Korea, Greece, and Italy, often build subways very cheaply. Germany, for all its stereotype of efficiency, has high costs and some dysfunctional decisionmaking in what to build. Singapore, the self-styled most efficient government, pays its transport minister more than a million dollars per year to make excuses for why it has such high construction costs.

In the Nordic countries, the stereotype is correct: those countries have transparent, clean governments, and also build infrastructure cheaply.

Subway tunnels

All four mainland Nordic capitals have recent or ongoing metro expansion projects:

Stockholm just opened Citybanan, a regional rail connection including 6 km of tunnel with two deep stations in Central Stockholm and a 1.4 km bridge. The total cost was 16.8 billion SEK in 2007 terms, which in today’s PPP terms is about $330 million per km. It’s expensive for a suburban subway but not for regional rail.

Copenhagen is currently wrapping up construction on the fully underground, driverless City Circle Line. It is a circular but not circumferential line through city center. With repeated schedule slips, the budget is now 24.8 billion DKK, or $3.4 billion in PPP terms, which is $220 million per km.

Stockholm is expanding its metro in three directions. The fully underground extensions are together 19 km and 22.4 billion SEK, which in PPP terms is $130 million per km.

Helsinki has just opened an expansion of its metro westward to Espoo. This is a 13.5 km, 8-station fully underground line with a water crossing. After cost overruns, the current cost estimate is 1,186 million, which is in PPP terms $115 million per km.

Oslo recently opened a short connection, called Lørenbanen. It’s 1.6 km long and includes a single new station, for a total of NOK 1.33 billion, including 150 million for modernization of an existing connecting line. In PPP terms this is just $90 million per km in today’s money.

Other rail infrastructure

Sweden is investing heavily in mainline rail modernization. This includes a planned high-speed rail network connecting the country’s three biggest cities, which are spaced far apart and not on a line, requiring the total system to be 740 km long. The cost projection as of 2015 is 125 billion SEK, which in PPP terms is $14 million per km; I do not know if it is in 2015 prices or expected year of construction prices. This cost figure is comparable to that of Madrid-Barcelona and about half the at-grade norm for Europe.

Sweden is simultaneously investing in its mainline network, rather than neglecting it in favor of just HSR the way France is. A document from 2009 lists some of these on p. 38 based on the national plan of 2010-21, which did not include HSR. Of note, two full double-track projects are coming it at about $10 million per km or slightly more. In contrast, in Berlin, suburban S-Bahn double-tracking is around twice as expensive per the list on PDF-pp. 73-77 of the official wishlist.

In Denmark, a recent double-tracking project cost 675 million DKK for 20 km, or $4.6 million per km, even cheaper than in Sweden. The project includes not just double track but also an upgrade to 160 km/h.

Denmark is also investing heavily in electrification – see here for a list of projects, without costs. Costs for some of these projects are provided by Railway Gazette. The Fredericia-Aalborg line is 249 km and 4.7 billion DKK, the Roskilde-Kalundborg line is 56 km and 1.2 billion DKK, and the Esbjerg-Lunderskov line is 57 km and 1.19 billion DKK; all three lines are double-track. The longer line is $2.6 million per km, the shorter two are $2.9 million. This is much cheaper than in the core Anglosphere but more expensive than projects for which I have data in France, Israel, and New Zealand.

It’s cheap, but do people ride it?

Absolutely. Low construction costs can occur for projects that nobody has any reason to build, they’re so low-ridership, while some high-cost projects remain cost-effective if they have extremely high ridership, like Second Avenue Subway Phase 1.

In the case of the Nordic capitals, the recent extensions are well-patronized. The ridership prognosis for the City Circle Line is 289,000 per weekday, which means its cost is $11,800 per rider. The link above for the Stockholm T-bana extension projects 170,000 riders per day, which I believe means weekday rather than literal day; in that case, the projected cost per rider is $14,500. Løren’s ridership is 8,000 per day, which one former resident says is just boardings without alightings, which means total ridership is actually 16,000, making the cost of the line just shy of $9,000 per rider. And Helsinki’s West Metro is projected to get 100,000 daily riders, which means its cost is about $15,500 per rider.

Moreover, Stockholm’s overall use of public transportation is very healthy. The first 6 pages of this PDF comprise a report on modal split in Stockholm, out of all trips, not just work trips. In 2015, 32% of all trips in Stockholm County were by public transport, 38% were by car, 9% were by bike, and 16% were on foot. There had been a notable shift from cars to the other modes since 2004.

Converting this statistic to work trip mode share, the most stable metric and the one reported for the US, Canada, UK, and France, requires some additional work. However, where both statistics are available, they do provide some insight: in Hamburg in 2008, the overall car mode shares for all trips and for just work trips were similar (48% for work trips vs. 42% for all trips in the city, 65% vs. 63% in the suburbs); work trips alone exhibit much higher transit mode share (33% vs. 18% in the city, 16% vs. 8% in the suburbs), at the expense of non-motorized trips, which are disproportionately for short errands. It is very likely that the work trip public transport mode share in Stockholm County is comparable to Ile-de-France’s 43%, in a metro area one fifth the size.

Transit ridership in the other Nordic capitals is weaker, though still impressive for their size. Copenhagen lags in transit but has a strong bike network. Oslo had 118 million metro riders in 2017 (source, PDF-p. 31 – per same link you can also see the operating costs per car-km work out to just short of PPP$4, compared with a typical first-world range of $4-7), plus some additional commuter rail ridership (65 million nationwide, not just around Oslo). Helsinki had 63 million annual metro passengers in 2015, before the extension opened, and somewhat fewer additional commuter rail passengers, for a total ridership of perhaps 120 million. Both of the smaller cities have about the same metro area rail ridership per capita as New York, which is about fifteen times their size.

What does this mean?

Scandinavia has a reputation for efficient government at home as well as abroad. Right-wing pundits are far more likely to look for aspects of its governance that play to their desire for privatization, such as Sweden’s school voucher system or the contracting out of urban rail, than to assert that Scandinavia is a socialist failure. Unlike autocracies that have cultivated such reputation, the Nordic countries fully deserve this praise when it comes to building infrastructure cost-effectively. Sweden appears to consistently build rail for half the per-unit cost of Germany.

And yet, I don’t see that much praise for Nordic infrastructure. There are people in the English-speaking world making grandiose claims about how democratic countries need to be more like China and about how authoritarianism is just more efficient. I don’t know of any making that claim about how Nordic social democracy is more efficient, with its depoliticized state apparatus, multiparty elections, high levels of transparency, bureaucratic legalism, and near-universal collective bargaining.

Across all levels of public transportation investment, from high-speed rail down to routine track upgrades, we see inexpensive, efficient projects in the Nordic countries. They achieve high levels of rail usage without megacities in which only masochists drive, and keep expanding their networks in order to complete the green transition. Public transit managers in not just the laggard that is the US but also Germany and other relatively solid countries should make sure to study how things work in Scandinavia and how they can import Nordic success.

Growth and Environmentalism

I’ve been asked to write about the issue of growth versus no growth. This is in the context of planning, so broader questions of degrowth are not within this post’s main scope. Rather, it’s about whether planning for more growth is useful in combating pollution and greenhouse gas emissions. The answer is yes, though the reasoning is subtle. Smart growth is the key, and yet it’s not a straightforward question of transit construction and transit-oriented development helping the environment; it’s important to figure out what the baseline is, since a large urban apartment still emits more CO2 than the closets people end up living in in parts of San Francisco and New York.

The argument for growth specifically is that a high baseline level of growth is what enables smart growth and TOD policies. Vancouver’s secular increase in transit usage, and to a lesser extent the ongoing revival in Seattle and that of Washington in the 2000s, could not happen in a region with Midwestern population growth.

Smart growth vs. no growth

VTPI has many references to studies about smart growth here. The idea of smart growth is that through policies that encourage infill development and discourage sprawl, it’s possible to redirect the shape of urban areas in a greener direction. Here’s one specific VTPI paper making this comparison directly on PDF-p. 3.

Unfortunately, the reality is that there are at least three poles: in addition to sprawl and smart growth, there is no growth. And moreover, many of the bureaucratic rules intended to encourage smart growth, such as comprehensive zoning plans, in fact lead to no growth. The following table is a convenient summary of housing permitting rate vs. my qualitative impression of how smart the growth is.

The permitting rate is absolute, rather than relative to birth rates, immigration, and internal migration pressure as seen in average incomes. Tokyo’s permitting rate is similar to Vancouver’s – Tokyo Prefecture’s rate of 10 annual units per 1,000 people and so is Metro Vancouver’s, but Japan’s population is falling whereas Canada’s is rising. See also European rates linked here and American rates here.

The infill vs. sprawl dimension is qualitative, and combines how transit-oriented the construction is with whether the development is mostly in the city or in the suburbs. Berlin’s suburbs are shrinking due to the depopulation of East Germany, and growth in the suburbs of Tokyo and West Germany is weak as well, but city growth is going strong. Paris is building a lot of public transit and is very dense, but there’s more development per capita in the suburbs, and likewise in California most development is in exurbs rather than in central cities; Seattle is penalized for having bad transit, and Atlanta for having no transit, but in both there’s a lot more development in the city than in the suburbs. Stockholm and Vienna have growth all over and excellent public transit.

The significance of the diagram is that by the standards of European transit cities, California is not an example of smart growth, but of no growth.

Shaping growth

In the high-growth area of the diagram, the most interesting case is not Tokyo, but Vancouver and Seattle. In these cities, there is a transit revival. Metro Vancouver’s mode share went up from 13% in 1996 to 20% on the eve of the Evergreen extension’s opening. Moreover, for most of this period Vancouver saw car traffic decrease, despite high population growth. Metro Seattle’s transit revival is more recent but real, with the mode share rising from the “no transit” to “bad transit” category (it is 10% now).

Both cities invested heavily in transit, Vancouver much more so than Seattle, but it was specifically transit aimed at shaping growth. Before the Expo Line opened, Downtown had few skyscrapers, Metrotown did not yet exist, New Westminster had a low-rise city center, and the areas around Main Street-Science World, Joyce-Collingwood, and Edmonds were nonresidential and low-density. The combination of fast growth and rapid transit ensured that new development would add to transit ridership rather than to road traffic. Moreover, the strong transit spine and growing employment at transit-oriented centers meant existing residents could make use of the new network as well.

The same situation also exists in Europe, though not on the same transformative scale as in Vancouver, since the cities in question came into the new millennium with already high transit usage. Stockholm just opened a regional rail tunnel doubling cross-city capacity and is expanding its metro network in three directions. This program is not available to lower-growth cities. Berlin has grandiose plans for U-Bahn expansion and has even safeguarded routes, but it has no active plans to build anything beyond the U5-U55 connection and S21 – the city just isn’t growing enough.

Public transit without growth

By itself, growth is not necessary for the existence of a robust transit network. Vienna proper had more people on the eve of WW1 than it has today, though in the intervening generations there has been extensive housing construction, often publicly subsidized (“Red Vienna”), increasing the working class’s standard of living. However, in a modern auto-oriented city – say, anything in North America other than New York – it is essential.

This becomes clear if we look at the next tier of American cities in transit usage after New York, that is Chicago, San Francisco, Washington, and Boston. Washington is the odd one – it had a transit revival before the Metro collapse of this decade, and got there through TOD in choice locations like Arlington. The others inherited a prewar transit network and made some improvements (like the Transbay Tube replacing the Key System), but froze urban development in time. Essentially all postwar development in those cities has been sprawl. Chicago had big enough a core to maintain a strong city center, but outside the Loop the job geography is very sprawled out. Boston and the Bay Area sprouted suburban edge cities that became metonyms for their dominant industries, with a transit modal share of about 0%.

Chicago’s transportation situation is difficult. The city is losing population; some specific neighborhoods are desirable and some around them are gentrifying, but the most optimistic prognosis is that it’s akin to New York in the 1970s. If there’s no population to justify a public transit investment today, there won’t be the population to justify it tomorrow. Any investment has to rely on leveraging the city’s considerable legacy mainline network, potentially with strategic cut-and-cover tunneling to connect Metra lines to each other.

And if Chicago’s situation is difficult, that of poorer, smaller cities is most likely terminal. Detroit’s grandiose plans are for urban shrinkage, and even then they run into the problem that the most economically intact parts of the region are in low-density suburbs in Oakland County, where nobody is going to agree to abandonment; the shrinkage then intensifies sprawl by weakening the urban core. Even in European cities where the shrinkage is from the outside in, there’s no real hope for any kind of green revival. Chemnitz will never have rapid transit; its tram-train has 2.6 million annual passengers.

Idyll and environmentalism

The environmental movement has from the start had a strong sense of idyll. The conservationism that motivated John Muir and Teddy Roosevelt was about preserving exurban wilderness for rich adventurers to travel in. The green left of the 1960s dropped the explicit classism but substituted it for new prejudices, like the racism embedded in population control programs proposed by Westerners for the third world. Moreover, the romantic ideals of Roosevelt-era environmentalism transformed into small-is-beautiful romanticism. Even Jane Jacobs’ love for cities was tempered by a romanticism for old low-rise neighborhoods; she predicted the Upper West Side with its elevator buildings would never be attractive to the middle class.

But what’s idealized and what’s green are not always the same. Lord of the Rings has a strong WW1 allegory in which the hobbits (Tolkien) leave the Shire (the English Midlands) to go to war and come back to find it scoured by industrialization. But on the eve of WW1, Britain was already a coal-polluted hellscape. Per capita carbon emissions would remain the same until the 1970s and thence fall by half – and in the first three quarters of the 20th century the fuel source shifted from coal to oil, which is less polluting for the same carbon emissions. The era that Tolkien romanticized was one of periodic mass deaths from smog. The era in which he wrote was one in which public health efforts were undertaken to clean up the air.

Likewise, what passes for environmentalism in communities that openly oppose growth freezes the idyll of postwar America, where suburban roads were still uncongested and the middle class had midsize houses on large lots. But American greenhouse gas emissions per capita were the same in 1960 as today, and had been the same in good economic times going back to the eve of the Great Depression. Only centenarians remember any time in which Americans damaged the planet less than they do today, and “less” means 14 tons of CO2 per capita rather than 16.5.

The upshot is that in the developed world, environmentalism and conservation are opposing forces. Conservation means looking back to an era that had the same environmental problems as today, except often worse, and managed to be poorer on top of it all.

Growth and environmentalism

Strictly speaking, growth is not necessary to reduce emissions. The low-growth city could just as well close its road network, ban cars, and forbid people to use electricity or heating generated by fossil fuels – if they’re cold, they can put on sweaters. But in practice, low-emission developed countries got to be where they are today by channeling bouts of economic growth toward clean consumption of electricity as well as transportation. Regulatory coercion and taxes that inconvenience the middle class are both absolutely necessary to reduce emissions, and yet both are easier to swallow in areas that have new development that they can channel toward green consumption.

The environmentalist in the Parises and Stockholms has the easiest time. Those cities have functioning green economies. There are recalcitrant mostly right-wing voters who like driving and need to be forced to stop, but a lifestyle with essentially no greenhouse gas emissions except for air travel is normal across all socioeconomic classes. The Vancouvers are not there but could get there in a generation by ensuring future development reinforces high local density of jobs and residences. The pro-development policies of the Pacific Northwest are not in opposition to the region’s environmentalism but rather reinforce it, by giving green movements a future to look forward to.

The environmentalist in the Clevelands and Detroits has the hardest time. It’s even worse than in the Chemnitzes – Saxony may be a post-industrial wasteland with 10% fewer people now than it had in 1905, but it’s coming into the 21st century with German emissions rather than American ones. These are cities with American emissions and economies based substantially on producing polluting cars, propped by special government attention thanks to the American mythology of the Big Three.

But whereas the Rust Belt has genuine problems, NIMBYvilles’ low growth is entirely self-imposed. New York and Los Angeles have the same per capita metro housing growth as Detroit, but only because they choose stasis; where the price signal in Detroit screams at people to run away, that in New York and California screams to build more housing. Their political institutions decided to make it harder to build any green future not only for their current residents but also for tens of millions who’d like to move there.

Transit-Oriented Suburbs

I did a Patreon poll last month with three options, all about development and transit: CBDs and job concentration in middle-income cities (e.g. auto-oriented Bangkok and Istanbul don’t have transit-oriented Shanghai’s CBD formation), dense auto-oriented city neighborhoods (e.g. North Tel Aviv), and transit-oriented low-density suburbia. This is the winning option.

In every (or almost every) city region, there’s a clear pattern to land use and transportation: the neighborhoods closer to the center have higher population density and lower car use than the ones farther away. Moreover, across city regions, there is such a strong negative correlation between weighted density and auto use that exceptions like Los Angeles are notable. That said, the extent of the dropoff in transit use as one moves outward into suburbia is not the same everywhere, and in particular there are suburbs with high transit use. This post will discuss which urban and transportation policies are likely to lead such suburbs to form, in lieu of the more typical auto-oriented suburbs.

What is a suburb?

Definitions of suburbia differ across regions. Here in Paris, anything outside the city’s 1860 limits is the suburbs. The stereotypical banlieue is in history, urban form, and distance from the center a regular city neighborhood that just happens to be outside the city proper for political reasons. It is hardly more appropriate to call any part of Seine-Saint-Denis a suburb than it is to call Cambridge, Massachusetts a suburb of Boston.

So if Seine-Saint-Denis is not a suburb, what is? When I think of suburbia, my prototype is postwar American white flight suburbs, but stripped of their socioeconomic context. The relevant characteristics are,

  • Suburbs developed at a time when mass motorization was widespread. In the US, this means from around 1920 onward in the middle class and slightly later in the working class; in the rest of the developed world, the boundary ranges from the 1920s to the 1960s depending on how late they developed. Note that many stereotypical suburbs were founded earlier, going back even to the 19th century, but grew in the period in question. Brookline is famous for refusing annexation to Boston in 1873, but its fastest development happened between 1910 and 1930, straddling the 1920 limit – and indeed in other respects it’s borderline between a rich suburb and rich urban neighborhood as well.
  • Suburbs have low population density, typical of single-family housing. Aulnay-sous-Bois, at 5,100 people per km^2, is too dense, but not by a large margin. Beverly Hills, which has mansions, has 2,300, and Levittown, New York, probably the single best-known prototype of a suburb, has 2,900. The urban typology can mix in apartments, but the headline density can’t be dominated by apartments, even missing middle.
  • Suburbs are predominantly residential. They can have distinguished town centers, but as broad regions, they have to have a significant number of commuters working in the city. This rules out low-density central cities like Houston and Dallas (although their individual neighborhoods would qualify as suburbs!). It also rules out Silicon Valley as a region, which represents job sprawl more than residential sprawl.

The three criteria above make no mention of whether the area is included in the central city. Most of Staten Island qualifies as suburban despite being part of New York, but Newark fails all three criteria, and Seine-Saint-Denis and most of Hudson County fail the first two.

Where are suburbs transit-oriented?

I do not know of any place where suburban transit usage is higher than city center transit usage. In theory, this suggests that the best place to look for transit-oriented suburbia is the cities with the highest transit mode shares, such as Tokyo, Singapore, and Hong Kong (or, in Europe, Paris). But in reality, Singapore and Hong Kong don’t have areas meeting the density definition of suburb, and Tokyo has few, mostly located away from its vast commuter rail network. Paris has more true suburbs, but like Tokyo’s, they are not what drives the region’s high rail ridership. All four cities are excellent examples of high-density suburban land use – that is, places that meet my first and third definitions of suburbia but fail the second.

Instead, it’s better to look at smaller, lower-density cities. Stockholm and Zurich are both good models here. Even the central cities are not very dense, at 5,100 and 4,700 people per km^2. Moreover, both are surrounded by large expanses of low-density, mostly postwar suburbia.

Winterthur, Zurich’s largest suburb, is a mix of early 20th century and postwar urban typology, but the other major cities in the canton mostly developed after WW2. At the time, Switzerland was already a very rich country, and car ownership was affordable to the middle class. The story of the Zurich S-Bahn is not one of maintaining mode share through a habit of riding transit, but of running frequent commuter rail to suburbs that did not develop around it from the 1950s to the 70s.

In Stockholm, there is a prominent density gradient as one leaves Central Stockholm. I lived in Roslagstull, at the northern end of Central Stockholm, where the density is 30,000 people per km^2 and the built-up form is the euroblock. Most of the rest of Central Stockholm is similar in urban form and not much less dense. But once one steps outside the city’s old prewar core, density nosedives. City districts to the west and south, like Bromma and Älvsjö, go down to 3,000 people per km^2 or even a little less. A coworker who used to live in Kista described the area as American-style suburban. Beyond these city districts lie the other municipalities, which together form a sizable majority of the county’s population. Of those, a few (Solna, Sundbyberg) are somewhat above the density cutoff, but most are far below it.

In both Zurich and Stockholm, the city is much more transit-oriented than the suburbs. Stockholm’s congestion pricing was a city initiative; the suburbs banded together to oppose it, and eventually forced a compromise in which congestion pricing remained in effect but the revenue would be deeded to urban freeways rather than to public transportation.

And yet, neither city has a big transit use gradient – at least, not so big as Paris, let alone London or New York. Stockholm is expecting 170,000 daily metro trips from its expansion program, which barely touches Central Stockholm. Existing T-bana ridership on the suburban tails is pretty high as well (source, PDF-p. 13), as is ridership on commuter rail, which, too, barely touches Central Stockholm.

The structure of density

In my previous post, I complained that Los Angeles’s density has no structure, and thus public transit ridership is very low and consists predominantly of people too poor to buy a car. The situation in Stockholm and Zurich is the reverse. Density has a clear structure: within each suburb, there is a town center near the commuter rail station.

The histories of Zurich and Stockholm are profoundly different. Each arrived in its structure from a different route. In Zurich, the suburbs come from historic town centers that existed long before cars, often long before industrialization. 20th-century urban sprawl arrived in the form of making these historic villages bigger and bigger until they became proper suburbs. The geography helps rail-oriented suburbanization as well: the ridge-and-valley topography is such that urban sprawl forms ribbons served by commuter rail lines, especially in the southerly direction.

Stockholm’s topography is nothing like Zurich’s. There are water boundaries limiting suburb-to-suburb travel, but the same is true of New York, and yet Long Island, New Jersey, and Westchester are thoroughly auto-oriented. Instead, the structure of density came about because of government planning. Sweden built public housing simultaneously with the Stockholm Metro, so the housing projects were sited near the train stations.

This does not mean that the suburbs of Zurich and Stockholm are actually high-density. Far from it: the housing projects in the Stockholm suburbs are surrounded by a lot of parking and greenery, and the suburbs have extensive single-family housing tracts. However, the density is arranged to grade down from the train station, and there are small clusters of walkable apartment buildings in a small radius around each station. In Zurich the same structure came about with private construction and topography.

To the extent this structure exists elsewhere, it leads to higher low-density transit ridership too, for example in London and the Northeastern United States. Various West Coast American transit bloggers, like Jarrett Walker and Let’s Go LA, keep plugging the West Coast grid over the Northeastern hierarchy of density. But this hierarchy of suburbs that formed around commuter rail to the CBD produces transit ridership that, while awful by Continental European standards, is very good by American ones. Many of the suburbs in question, such as in Westchester, have 15-20% of their commuters choose transit to get to work.

Getting to higher numbers means reinforcing the structure of density and the transit that works in the suburbs, that is, regional rail (or a metro network that goes far out, like the T-bana, if that’s an option). Stations must be surrounded by development rather than parking, and this development should facilitate a somewhat transit-oriented lifestyle, including retail and not just housing. Jobs should be accessible from as many directions as possible, forming CBDs rather than haphazard town centers accessible only by road. Only this way can suburbia be transit-oriented.

Job Sprawl in the US vs. Europe

Both American and European cities have prominent central business districts with high job density. But when jobs sprawl beyond the CBDs, they do so in very different manners on the two sides of the Pond, which is both a cause and an effect of higher US automobile usage. Much of this job sprawl happens in places that people on the other side of the Pond would not recognize as part of The City. Besides the obvious misunderstandings, this can compromise the quality of analysis of urbanism and the transportation required to serve it. In short, the European model, for which my models are Stockholm and Paris, is that jobs sprawl contiguously from the CBD, enlarging its physical area, whereas the North American model, for which my models are New York and Washington, is that jobs leap large swaths of residential neighborhoods into auto-oriented suburbia.

CBDs and job density

Office towers are rare in European CBDs. Paris is largely built up to 6 to 9 stories, and the higher end is more common in residential areas like Nation than in the CBD, which stretches from Les Halles to Saint-Lazare and Etoile. Stockholm has a total of five towers in its center, none especially tall. Contrary to the common European belief that high-rises don’t add density, the mid-rise character of most European CBDs leads to a real limit on their ability to agglomerate. The job-densest arrondissement of Paris, the 2nd, has 60,000 jobs in a square kilometer (look for table EMP T6 here); Midtown Manhattan has about 800,000 jobs in 4 square kilometers.

Not all jobs are in the CBD. Some are local community facilities, such as schools, supermarkets, and hospitals. But even more exportable jobs are not all in the CBD. Some industries cluster in sections of the CBD (such as advertising on Madison Avenue in New York or, traditionally, the media on Fleet Street in London), and similarly some cluster in off-CBD locations, perhaps near one firm that located idiosyncratically. In the other direction, not even the job density of Midtown can contain every workplace that wants a central location, and this pushes out firms that can’t compete for CBD office rents. The difference between the North American and European models is where these firms are likely to locate.

Contiguous sprawl

In both Paris and Stockholm, the solution to the restricted job density of their city centers is, superficially, high-rise clusters in a particular suburban place: La Defense in Paris, Kista in Stockholm. The job density at the center of La Defense is actually higher than in the 2nd arrondissement, though it drops drastically outside the very center, whereas the Paris CBD maintains a density of about 50,000 jobs per km^2 over 4 or 5 square kilometers. In both cases, this leads to spatial inequality: in Paris, the richest suburbs are in the west and southwest, and La Defense is west of the city; in Stockholm, Kista itself is surrounded by working- and middle-class areas, and the favored quarter is separated from it by a lake, but the ill-favored quarter to the south is the farthest away.

However, there is much more to Paris employment than the CBD and suburban office towers. Paris has a total of 1.8 million jobs, with only around one eighth to one sixth of them in the CBD. There are corporate headquarters in La Defense and a number of other suburbs on the RER, but there are job clusters all over the city. My arrondissement, the 12th, has 120,000 jobs in a little more than 6 square kilometers, giving it the same job density as is average for the city. According to OnTheMap, Upper Manhattan, defined to be north of East 96th and West 110th Streets, has 150,000 jobs in 19 square kilometers, and the Upper East and West Sides, defined to be north of 62nd Street so as to exclude Columbus Circle jobs, have a total of 175,000 jobs in 9 square kilometers. While the Upper East and West Sides hold their own, in large part thanks to the hospital cluster around Weill-Cornell, Upper Manhattan does not.

These clusters in Paris are everywhere. In my arrondissement the cluster in question is Bercy, home to the Ministry of Finance; there’s also the university cluster in the Latin Quarter, an under-construction judicial cluster around Clichy-Batignolles, and high-end professional services spillover west of the CBD in the 16th and 17th arrondissements. In effect, office uses are sprawling into otherwise-residential neighborhoods.

In Stockholm, the same situation occurs. Spotify is headquartered two T-Bana stops north of T-Centralen, a short walk from where I used to live in Roslagstull (in fact, one of the people viewing my apartment as I was leaving it worked there). There’s also a prominent peak travel flow of students heading to KTH and the University on the trains from points south. In the south, Södermalm has its own secondary CBD around Slussen, the second busiest T-Bana station after T-Centralen.

Office park sprawl

North American cities do not have high overall job density in the core when one counts both the CBD and surrounding inner neighborhoods, which are typically entirely bedroom communities like Upper Manhattan. Instead, there is discontinuous job sprawl: jobs hop over residential areas into farther-away places, typically suburban office parks. The most famous in American urbanist discourse is Tysons Corner in Northern Virginia, but the Washington metropolitan area is generally replete with edge cities, including Reston, Bethesda, and Silver Spring, all located in the northern and western favored quarters of the region. Kista is really a high-rise version of these edge cities.

Washington is the purest example of office job sprawl. However, even there, there is a complication: there are some nearer job clusters like the Pentagon. New York and other large American cities are the same, with even more complications like this. In New York, the in-state side of the metro area has large suburban job clusters such as White Plains and Stamford, but the New Jersey side includes the formerly independent Downtown Newark, contiguous job sprawl in Jersey City directly facing Lower Manhattan, and very decentralized job sprawl in Middlesex County, contrasting with the centralized office sprawl of White Plains.

Robert Lang and Jennifer Lefurgy call Central Jersey edgeless cities and White Plains and Tysons edge cities. While edge cities exist in Europe, edgeless cities do not. Exurban retail in France resembles American exurban retail, with Carrefour inventing the hypermarket at the same time Wal-Mart did, but there is almost no equivalent of the small American office park. The closest I am aware of, Sophia-Antipolis, is an edge city with a large concentration of jobs, just built at automobile scale without any walkability.

New York is large enough to have an intermediate form: namely, a secondary CBD that’s not contiguous with the main city center. Downtown Brooklyn arose as such a CBD, serving Brooklyn, even though it’s contiguous with Lower Manhattan across the water. Jamaica is the best example, as it is quite far from Manhattan. La Defense should be put in this category as well – it is contiguous with the dense built-up area, if not with the CBD itself, and it is closer to Les Halles than Jamaica is to Midtown.

Favored quarters

There are multiple instances of large American firms moving their entire headquarters to be close to where the CEO lives. IBM moved to Armonk and General Electric moved to Fairfield, both leaving New York, to avoid making executives drive in Manhattan traffic. In Europe, too, the edge cities tend to be in rich areas. The corporate headquarters around Paris cluster in La Defense and to a lesser extent northwestern and southern suburbs, and not in Seine-Saint-Denis.

This is a straightforward consequence of the fact that rich Americans left city centers starting in the early 20th century, culminating in middle-class white flight in the 1950s, whereas Paris and Stockholm remain richer than their suburbs. The inhabitants of the 16th arrondissement of Paris are unlikely to be interested in job sprawl. Instead, the Paris CBD is slowly migrating westward, as retail and office rents at the western end (Etoile) are higher than in the center (the Opera) and eastern end (just west of Les Halles).

One would suspect that in American cities that are richer than their suburbs, the phenomenon of job sprawl would not occur. The problem is that there is no clean example today. Boston is still poorer than its suburbs; Cambridge is quite rich, but is functionally one favored-quarter wedge. San Francisco is overall richer than most of its suburbs, but really the entire strip of land from San Francisco down to San Jose is rich, and at any rate Silicon Valley formed in a then-independent metro region, rather than sprawling out of the center the way White Plains and Tysons Corner did.

However, as white flight is giving way to gentrification, and American cities are economically outgrowing their suburbs, this theory would predict that job sprawl should decrease, with more corporate jobs shifting back to the cities. This seems to indeed be happening: General Electric moved from Fairfield to Downtown Boston, and United-Continental moved its headquarters to the Sears Tower in the Chicago Loop; Aaron Renn periodically talks about the resorting of the American economy, in which the highest-end jobs are back to city centers whereas lower-end jobs are in the suburbs and smaller cities.

Is the US Europeanizing?

There is some evidence to suggest that American cities not only are reducing the extent of job sprawl in the highest pay categories, but also adopting the European pattern of contiguous CBD sprawl. This process is haphazard, and many urban boosters overrate the extent to which near-CBD locations like the West Loop in Chicago or the Seaport in Boston are attracting jobs, but these areas are nonetheless growing.

Boston is perhaps the best example of this trend. Locally, urban boosters anxiously talk about transportation connections to the Seaport, but the biggest action is happening in the other direction. Kendall Square is growing as the Cambridge CBD, with a cluster of tech firms, two stops out on the subway from the central transfer points. Boston is unique that Back Bay is a nearly-contiguous secondary CBD as well, based on extensive postwar urban renewal next to a rich residential neighborhood. This situation is especially notable given that both Cambridge and the Seaport are separated from the CBD by water, with unpleasant walking environments on the bridges, making the organic process of CBD extension more difficult.

Outside Boston, several more examples are notable. In San Francisco, tech jobs within the city cluster not in the Financial District but in the adjacent South of Market (“SoMa”) area. In Chicago, in addition to some growth in the West Loop, there is some job growth on the Near North Side. In New York, the tech jobs cluster in the Meatpacking District: the Google building, which I believe is the second largest Google office after the Googleplex, occupies the block between 8th and 9th Avenues and 15th and 16th Streets. But even before Google, there was growth in adjacent secondary CBDs across the water: Jersey City and Long Island City. Lang and Lefurgy’s writeup on edgeless cities classifies Jersey City as a secondary CBD rather than an edge city because “its context is old”: it’s built out of a near-CBD residential and industrial area, rather than developed from scratch near a road or rail intersection.

Starting last decade, urbanist writers in the United States noted that the US was Europeanizing in its pattern of rich cities and poor suburbs. Brookings was writing about suburbanization of poverty in 2010, describing a 2000-8 trend. The growth of near-CBD office clusters in Boston, New York, San Francisco, and Chicago suggests that the US is also Europeanizing in its pattern of how jobs spill over from the center. Instead of the traditional auto-oriented office park near the CEO’s residence, the highest-income, highest-prestige jobs in the US are decamping to the same near-CBD locations where they can be found in Paris or Stockholm, leaving the sprawl for the poor.

Transit and Scale Variance Part 2: Soviet Triangles

Continuing with my series on scale-variance (see part 1), I want to talk about a feature of transit networks that only exists at a specific scale: the Soviet triangle. This is a way of building subway networks consisting of three lines, meeting in a triangle:

The features of the Soviet triangle are that there are three lines, all running roughly straight through city center, meeting at three distinct points forming a little downtown triangle, with no further meets between lines. This layout allows for interchanges between any pair of lines, without clogging one central transfer point, unlike on systems with three lines meeting at one central station (such as the Stockholm Metro).

The name Soviet comes from the fact that this form of network is common in Soviet and Soviet-influenced metro systems. Ironically, it is absent from the prototype of Soviet metro design, the Moscow Metro: the first three lines of the Moscow Metro all meet at one point (in addition to a transfer point one station away on Lines 1 and 3). But the first three lines of the Saint Petersburg Metro meet in a triangle, as do the first three lines of the Kiev Metro. The Prague Metro is a perfect Soviet triangle; Lines 2-4 in Budapest, designed in the communist era (Line 1 opened in 1896), meet in a triangle. The first three lines of the Shanghai Metro have the typology of a triangle, but the Line 2/3 interchange is well to the west of the center, and then Line 4 opened as a circle line sharing half its route with Line 3.

Examples outside the former communist bloc are rarer, but include the first three lines in Mexico City, and Lines 1-3 in Tehran (which were not the first three to open – Line 4 opened before Line 3). In many places subway lines meet an even number of times, rather than forming perfect diameters; this is especially bad in Spain and Japan, where subway lines have a tendency to miss connections, or to meet an even number of times, going for example northwest-center-southwest and northeast-center-southeast rather than simply crossing as northwest-southeast and northeast-southwest.

But this post is not purely about the Soviet triangle. It’s about how it fits into a specific scale of transit. Pure examples have to be big enough to have three subway lines, but they can’t be big enough to have many more. Moscow and Saint Petersburg have more radial lines (and Moscow’s Line 5 is a circle), but they have many missed connections, due to poor decisions about stop spacing. Mexico City is the largest subway network in the world in which every two intersecting lines have a transfer station, but most of its lines are not radial, instead connecting chords around city center.

Larger metro networks without missed connections are possible, but only with many three- and four-way transfers that create crowding in corridors between platforms; in Moscow, this crowding at the connection between the first three lines led to the construction of the Line 5 circle. In many cases, it’s also just difficult to find a good high-demand corridor that intersects older subway lines coherently and is easy to construct under so much older infrastructure.

The result is that the Soviet triangle is difficult to scale up from the size class of Prague or Budapest (not coincidentally, two of the world’s top cities in rail ridership per capita). It just gets too cumbersome for the largest cities; Paris has a mixture of radial and grid lines, and the Metro still undersupplies circumferential transportation to the point that a circumferential tramway that averages 18 km/h has the same ridership per km as the New York City Subway.

It’s also difficult to scale down, by adapting it to bus networks. I don’t know of any bus networks that look like this: a handful of radial lines meeting in the core, almost never at the same station, possibly with a circular line providing crosstown service. It doesn’t work like this, because a small-city bus network isn’t the same as a medium-size city subway network except polluting and on the surface. It’s scaled for minimal ridership, a last-resort mode of transportation for the poorest few percent of workers. The frequency is a fraction of the minimum required to get even semi-reasonable ridership.

Instead, such networks work better when they meet at one city center station, often with timed transfers every half hour or hour. A crosstown line in this situation is useless – it cannot be timed to meet more than one radial, and untimed transfers on buses that come every half hour might as well not even exist. A source who works in planning in Springfield, Massachusetts, a metro area of 600,000, explained to me how the Pioneer Valley Transit Authority (PVTA) bus system works, and nearly all routes are radial around Downtown Springfield or else connect to the universities in the area. There are two circumferential routes within Springfield, both with horrifically little ridership. Providence, too, has little to no circumferential bus service – almost every RIPTA bus goes through Kennedy Plaza, except some outlying routes that stay within a particular suburb or secondary city.

The principle here is that the value of an untimed transfer depends on the frequency of service and to some extent on the quality of station facilities (e.g. shelter). Trains in Prague come every 2-3 minutes at rush hour and every 4-10 minutes off-peak. When the frequency is as low as every 15 minutes, transferring is already questionable; at the typical frequency of buses in a city with a bus-based transportation network, passengers are extremely unlikely to do it.

This raises the question, what about denser bus networks? A city with enough budget for 16 buses running at once is probably going to run 8 radii (four diameters) every half hour, with a city-center timed transfer, and service coverage extending about 24 minutes out of the center in each direction. But what happens if there’s enough budget for 60 buses? What if there’s enough budget for 200 (about comparable to RIPTA)?

Buses are flexible. The cost of inaugurating a new route is low, and this means that there are compelling reasons to add more routes rather than just beef up frequency on every route. It becomes useful to run buses on a grid or mesh once frequency rises to the point that a downtown timed transfer is less valuable. (In theory the value of a timed transfer is scale-invariant, but in practice, on surface buses without much traffic priority, schedules are only accurate to within a few minutes, and holding buses if one of their connections is late slows passengers down more than not bothering with timing the transfers.)

I know of one small city that still has radial buses and a circular line: Växjö. The frequency on the main routes is a bus every 10-15 minutes. But even there, the circular line (bus lines 2 and 6) is a Yamanote-style circle and not a proper circumferential; all of the buses meet in the center of the city. And this is in a geography with a hard limit to the built-up area, about 5-6 km from the center, which reduces the need to run many routes in many different directions over longer distances (the ends of the routes are 15-20 minutes from the center).

There’s also a separate issue, different from scale but intimately bundled with it: mode share. A city with three metro lines is capable of having high transit mode share, and this means that development will follow the lines if it is given the opportunity to. As the three lines intersect in the center, the place for commercial development is then the center. In the communist states that perfected the Soviet triangle, buildings were built where the state wanted them to be built, but the state hardly tried to centralize development. In Stockholm, where the subway would be a triangle but for the three lines meeting at one station, the lack of downtown skyscrapers has led to the creation of Kista, but despite Kista the region remains monocentric.

There is no chance of this happening in a bus city, let alone a bus city with just a handful of radial lines. In a first-world city where public transit consists of buses, the actual main form of transportation is the car. In Stockholm, academics are carless and shop at urban supermarkets; in Växjö, they own cars and shop at big box stores. And that’s Sweden. In the US, the extent of suburbanization and auto-centricity is legendary. Providence has some inner neighborhoods built at pedestrian scale, but even there, car ownership is high, and retail that isn’t interfacing with students (for example, supermarkets) tends to be strip mall-style.

With development happening at automobile scale in smaller cities with smaller transit networks, the center is likely to be weaker. Providence has more downtown skyscrapers than Stockholm, but it is still more polycentric, with much more suburban job sprawl. Stockholm’s development limits in the center lead to a smearing of commercial development to the surrounding neighborhoods (Spotify is headquartered two stops on the Green Line north of T-Centralen, just south of Odengatan). In Providence, there are no relevant development limits; the tallest building in the city is empty, and commercial development moves not to College Hill, but to Warwick.

With a weaker center, buses can’t just serve city center, unless the operating budget is so small there is no money for anything else. This is what forces a bus network that has money for enough buses to run something that looks like a transit network but not enough to add rail to have a complex everywhere-to-everywhere meshes – grids if possible, kludges using available arterial streets otherwise.

This is why bus and rail networks look so profoundly different. Bus grids are common; subway grids don’t exist, except if you squint your eyes in Beijing and Mexico City (and even there, it’s much easier to tell where the CBD is than by looking at the bus map of Chicago or Toronto). But by the same token, the Soviet triangle and near-triangle networks, with a number of important examples among subway network, does not exist on bus networks. The triangle works for cities of a particular size and transit usage intensity, and only in rapid transit, not in surface transit.