Category: Urbanism

European Urbanism and High-Speed Rail

Europe has a number of strong national high-speed rail networks, providing much inspiration internally as well as abroad, including in the United States. With Americans looking at an infrastructure bill including high-speed rail funding, there’s a lot of discussion about what can port, hence my proposal map. That said, caution is required when doing naive comparisons with Europe. European urbanism doesn’t work the same as American urbanism, in two ways. First, European cities are more compact and transit-oriented than most American cities, which is why I somewhat discount American lines unless at least one city connected has public transit. And second, Europe has more, smaller cities than the rest of the urbanized world. This post concerns the second issue.

French and American urbanism: an example

A few months ago I poked around European and East Asian metro area lists. The upshot is that whereas in the three East Asian democracies 70% of the population lives in metropolitan areas larger than 1 million, in France only 33% does, and the median resident sorted by metro area size lives in a metro region of 350,000.

We can apply the same analysis to the United States. At the CSA level, the median American lives in Sacramento, population 2.6 million, and 68% live in metro areas of at least 1 million; at the MSA level, the median is Milwaukee, population 1.6 million, and 56% live in metro areas of at least 1 million. American metropolitan areas are unusually weakly-centered, especially at the CSA level, but otherwise they’re pretty typical of the urbanized world; it’s Europe that’s unusual in having such small cities.

The upshot is that people who are not used to this peculiarity of Europe who look at a map of European cities focus on million-plus metro areas, which are not the whole story here, especially not in France. This makes Europe look emptier than it is, which can lead people to overrate how much ridership a high-speed rail network would have at a fixed population.

France and the Midwest

Scott Hand posted a map on Twitter superimposing France on the Midwest with Chicago taking the place of Paris, arguing that they are similar in population and area:

This is a good sanity check: your Midwestern network should be of comparable magnitude to the TGV network, rather than much larger. It’s easy to say, Lyon has 2.5 million people, Detroit has 5 million people, so clearly a line to Detroit is twice as good as one to Lyon, right? But no: French urbanism supplies many more small cities, which must be accounted for as well. At the end of the day, the populations are similar, even though, in addition to Chicago, the map has three cities (Detroit, St. Louis, Cleveland) with larger metro areas than Lyon and six more larger than Marseille (Milwaukee, Indianapolis, Nashville, Cincinnati, Columbus, Pittsburgh).

The LGV Sud-Est

It’s tempting to compare Paris-Lyon to Chicago-St. Louis. Yonah Freemark did this in 2009, and Jarrett Walker already pointed out in comments that the LGV Sud-Est was always about much more than this. On hindsight, I’ll add that even that sells the LGV Sud-Est short. High-speed rail between Paris and Lyon unlocked fast service from Paris to not just Lyon but also the following metro areas, all with 2016 populations:

  • Dijon (385,000), demoted from the PLM mainline to a branch but still served
  • Grenoble (688,000)
  • Saint-Etienne (520,000)
  • Chambéry (225,000)
  • Annecy (236,000)
  • Valence (187,000)
  • Vienne (115,000)
  • Bourg-en-Bresse (128,000), not on any direct train but still close enough by regional connection or car

What’s more, TGVs would branch from Part-Dieu along legacy lines to serve these smaller cities, albeit at low frequency. Now, with the LGV extending as far south as Marseille, Valence has a through-station on an LGV just outside the built-up area. There’s also Lyria service to thee major Swiss cities; Geneva, a metro area of 1 million, lies on a low-speed extension of the LGV Sud-Est, 3:11 from Paris.

Other than Geneva, which is invisible on the map because it is farther away, the other cities listed are all very small. In the United States, people don’t usually think of metropolitan areas of such size as urban, because they are extremely dispersed and socially identify as not-urban, and because metropolitan America operates at much larger size classes. But they have recognizable urban cores and their populations must be put into any ridership model trying to train data on TGV ridership. In fact, a gravity model with exponent 0.8 predicts that the combined TGV ridership from Paris to all the above cities, excluding Lyon, is nearly twice the ridership on Paris-Lyon.

And in this context, Chicago-St. Louis simply doesn’t compare. St. Louis is somewhat larger than Lyon, yes, but within 60 km, within which radius Lyon has independent Saint-Etienne, Vienne, Bourg, and Mâcon, St. Louis only has its own exurbs. To find a proper Midwestern comparison for the LGV Sud-Est and its extensions toward Marseille, one must go east of Chicago, toward Detroit and Cleveland. Within 60 km Detroit too only has its own CSA plus Windsor, but that CSA has 5 million people, and the same line also reaches Cleveland (CSA population 3.5 million), Toledo (900,000), and Pittsburgh (2.6 million) and points east.

What this means

Having fewer, larger cities doesn’t make it harder to build high-speed rail. On the contrary – it’s easier to serve such a geography. Asia lives off of such geography; Japan and Taiwan serve nearly their entire populations on just a single line, and Korea does on one mainline with a branch. An Asianized France would be able to serve nearly its entire population on the LGV network as-is without needing low-frequency branches to Chambéry- and Valence-scale cities, and an Asianized Germany would be able to just build an all-high-speed network and connect nearly everyone and not just half the population.

There are small cities that happen to lie on convenient corridors between larger cities, the way Valence is between Lyon and Marseille, or Augsburg and Ulm are between Stuttgart and Munich. Other small cities are close enough to large cities that they’re decently-served by a large city-focused rail network, like Saint-Etienne. Those cities are compact, so a large share of the population has access to the train – this is the explanation for the 0.8 exponent in the gravity model of ridership. But overall, most cities of that scale are strewn haphazardly around the country: examples include Limoges, Amiens, and Caen in France, and Osnabrück, Chemnitz, and Rostock here.

However, this doesn’t mean that, in analyzing the impact of population on ridership, we should just pretend the small cities don’t exist. They do, and they supply extra ridership that isn’t visible if one thinks city = metro area of 1 million or more. It’s an understandable way of thinking, but Europe has a lot of ridership generated from intermediate cities and from cities that have a regional rail connection to a big city or a less frequent direct intercity train, and the models have to account for it.

So yes, that the US has so many large-by-European-standards cities means high-speed rail would work well there. However, it equally means that a naive model that just says “this looks like the LGV Sud-Est” would underperform. A better model has to account for specific city pairs. American city pairs still look okay, even with extreme levels of sprawl at the outer ends, but ultimately this means the US can have a network of approximately the same scope of the LGV network, rather than one that is much denser.

Marketing Public Transport is Unlike Marketing Cars

I’ve written before about how planning public transport differs from planning cars, and how the macroeconomics of producing good public transport differ from that of exporting cars. Another difference between the two modes is marketing. I don’t usually like talking about marketing – I prefer making things to selling them – but it’s relevant, because private-sector marketing is a huge industry, and sometimes marketers end up making decisions about public transportation, and some of those lead to counterproductive planning.

The main difference is that public transportation does not have competition the way private industry does. In many travel markets, for example rush hour travel to city center, it is a monopoly. In others, it isn’t, but it remains fundamentally different from the competition, whereas private-sector marketing generally involves competition between fairly similar products, such as different brands of cars or computers or supermarkets. This also means that trying to turn public transit into a competition between similar providers is overrated: it is bad from the perspective of good planning, but it turns the industry into something private-sector marketers are more familiar with, and is therefore at risk of being adopted (for example, with EU competition mandates) despite being counterproductive.

Brand identity

Companies that make products that are very similar to their competition engage in extensive marketing. Coke vs. Pepsi is the most cliché example, but different brands of cookies, fast food, cars, computers, and smartphones do the same. The differences between these brands are never zero: I can generally tell different brands of bottled water by taste, Samsung- and Sony-made Androids have some differences (let alone iPhones), and so on. But it’s not large either.

Objectively, the cost of switching firms is small, so marketers first of all spend enormous amounts of money on advertising, and second of all aim to create identity markers to impose an emotional cost on customers who switch: “I am a Mac.” If the small differences involve differences in price point, then this can include a marker of class identity; even if they don’t, there’s no shortage of ways to tell people what brand of alcohol or food or video game best fits their microidentity. Establishing brand identity also involves loyalty programs, like airline miles and hotel points: why compete when you can lock passengers into your airline alliance?

This can even bleed into product development to some extent. Microsoft’s embrace, extend, exterminate strategy was designed around getting people to switch to Microsoft products from competitors. This was not a marketing gimmick – the people who developed Excel made sure everything that Lotus 1-2-3 users were used to would also feature in Excel in order to reduce the cost of switching to Microsoft, before using Windows’ power to lock people into Office.

Mass transit is not like this

Public transportation competes with cars as a system. It has a monopoly in certain travel markets, namely rush hour travel to city center, but the existence of those markets itself comes from real estate competition, in which it is necessary to entice companies to choose to locate in city center rather than in a suburban office park. Of note, the following features, all unusual for private-sector competition, apply:

  • Competition is for the most part binary: public transportation versus cars. (Bikes complement transit.)
  • The public transit side of the competition has economies of scale because of the importance of frequency of arrival, and thus is harmed by any internal competition, whereas the car industry has different automakers and works just fine that way.
  • The service has very little customization – everyone rides the same trains. Attempts to introduce product differentiation are harmful because of the frequency effect.
  • The product is completely different from the competition – useful at different times of day, in different neighborhoods, for different destinations. Switching incurs costs of similar magnitude to those of migration.
  • Much of the competition is not for customers, but for development – city center development is good for public transit, sprawl is good for cars.
  • There is competition over public resources, which cannot be divorced from the mode even in an environment of privatization – someone still has to build roads and finance subways.

The consequences of mass transit Fordism

Public transportation is and remains a Fordist product – no product differentiation, highly regimented worker timetables, one-size-fits-all construction, vertical integration. The vertical integration aspects go even farther than early-20th century industry, covering infrastructure, timetables, the equipment, and development. User choice is extensive regarding where to go within the system – I have access to far more variety of products as a consumer and jobs as a worker in Berlin (and had even more in Paris) than I would have driving in a sprawl environment, but I can’t choose what brand of train to use.

This is particularly important when preferences are heterogeneous. Different users have different walking speeds, transfer penalties, idiosyncrasies about access to wifi on board, etc. Planning has to use averages, and for the most part this works without too many seams, but it means that the standard way private businesses use product differentiation doesn’t work.

Of note, this Fordism also exists for the road network, if not for the cars themselves. It’s just far less visible. Drivers may have different preferences that translate to different costs and benefits for a cloverleaf versus a four-level interchange, but engineers can’t have two sets of interchanges, they just build one based on criteria of traffic density. However, the experience of driving on the interchange is not visible as part of the system to the drivers, who occasionally grumble about traffic at a particular intersection but don’t see it as clearly as transit riders see specific transfer stations or modal questions like streetcar vs. subway.

How private-sector marketing can harm transit

Because mass transit is a single system for everyone, standard private-sector marketing schemes involve changes to service that harm the overall system.

Creating brand identification with a specific subgroup of users, such as when some private buses market themselves to tech workers with wifi and USB chargers and charge higher fares, and still can’t make money. Public transportation has to work on an any vehicle, any place, any time principle. Only a handful of hyper-frequent routes can take multiple brands without losing passengers due to the lower frequency of each brand, but on those routes the only reliable way to timetable service is to run on headway management in which case any vehicle can substitute for any vehicle, which means you can’t brand.

This is especially bad when the brands are different modes: bus, bike, streetcar, subway, commuter train. When some modes are marketed to the rich and others are to the poor, capacity is wasted and frequency within each class is lower. Moreover, infrastructure planning is weaker with such differentiation, because often a region or subclass will be close to the wrong mode, forcing expensive additional construction. The United States fails by running commuter rail just for the rich while subways are for the rest, while India fails by doing the exact opposite; both countries build unnecessary infrastructure and underinvest in intermodal integration as a result.

Less harmful but still likely to suck oxygen out of the planning room are various gimmicks, especially at the political level. For example, a program in the mold of cash-for-clunkers to pay people to sell their car and ride public transportation is a waste of money – the main cost of switching from cars to transit or vice versa is that in either case the set of destinations one can easily travel to changes.

Finally, because public transportation is a complex system, trading the need for inter-organization and interdepartmental organization for much lower overall provision costs, people who come into it from consumer product markets may miss some of the required connections. This is especially true of development – people who sell consumer products, including cars, don’t need to think how urban design has to look for their product to succeed. Even people who have heard of transit-oriented development may get it wrong; in the United States, it is common to build some apartment buildings next to a train station but neglect retail and local services, and YIMBY as a movement is at best indifferent to city center office towers.

How to Get Rich Off Low Construction Costs

A country or region that is good at manufacturing cars can export them globally and earn hard cash. But what about public transportation? How can a city that has the ability to build good, low-cost public transport get rich off of it? There is an answer, but it is more complicated than “export this,” mirroring the fact that public transport itself is a more complex system to run than cars. This in turn relates to housing growth rates and urban economies of scale, making this the most useful in a large city with high housing production rates, of which the best example is Seoul. The good news is that the world’s largest and richest cities could gain tremendously if they had better public transport as well as high housing growth rates.

Infrastructure is not exportable

I wrote more than two years ago about the difference between dirty and clean infrastructure. Cars, car parts, and oil are exportable, so the majority of the cost of cars as a system are exportable, making dedicated regions like Bavaria, Texas, and the Gulf states rich. Green tech is not like that – the bulk of the cost is local labor. A large majority of the operating costs of a subway system are local wages and benefits; in New York, depreciation on rolling stock is less than 10% of overall operating costs. Construction costs are likewise almost entirely local labor and management, which is why they are determined by where the project takes place, rather than by which engineering firm builds the project.

The upshot is that Madrid and other low-cost cities can’t just get rich by building other cities’ infrastructure for them. They can’t build turnkey systems for New York and London at Spanish prices – the problems with New York and London come from local standards, management, and regulations, and while a Spanish engineering firm could give valuable advice on what high-cost cities need to change, it’s not going to reap more than a fraction of the construction cost saving in consulting fees.

Good transit as an amenity

What a city can do with low-cost construction is build a large subway network like Madrid, and use that as infrastructure to help local economic production. This works as both a consumption amenity and a production amenity. As a consumption amenity, it enables people to commute without needing to own a car, which reduces living costs and lets employers get away with paying less in nominal terms; this is a bigger influence on local firms, because international ones tend to use cost of living adjustments that make profligate lifestyle assumptions and factor in car costs even in cities where car ownership is low, like Singapore or New York.

As a production amenity, public transit also enables work concentration in city centers. This is separate from the observation that it allows workers to commute more cheaply – if a large city produces in a concentrated center, then without rapid transit, workers can’t get in at all. About 23% of people entering the Manhattan core on a weekday do so by car per the Hub Bound Report, but at the peak hour, 8-9 am, this falls to 9%, because the road capacity is capped around 55,000 cars an hour and a maximum number of parking spots for them. Auto-centric cities of New York’s approximate size exist, not by building massive road capacity to support comparable city centers, but by not having strong city centers to begin with. Los Angeles has maybe 400,000 people in the widest definition of its central business district, where in the same area New York has more than 2 million – and Los Angeles’s secondary centers, like Century City, top in the mid-5 figures before they get completely choked with traffic.

So what a city can do with cheap infrastructure is build a large subway network and support a large high-rise central business district and then use that to produce more efficiently. This is possible, but more complex than just exporting cars or oil, because to export cars one just needs to be good at making cars, and to export oil one just needs to have oil underground, whereas to produce out of public transit one also needs a solid economy in other sectors that can make use of the better infrastructure. I suspect that this is why Southern Europe keeps not growing economically despite building high-quality public transport – the Madrid Metro is great but there isn’t enough of a private economy to make use of it.

The connection with development

To maximize the use of a subway for its economy, a city needs to make sure development can follow it. This means that city center needs high job density, which includes high-rise office towers at the busiest intersections, and many mid-rise office buildings in a radius of a few kilometers. Neither the typical European pattern in which there are few skyscrapers nor the American pattern in which there are skyscrapers for a few blocks and then the rest of the city is subject to strict residential zoning is ideal for this. It’s better to have a city whose central few square kilometers look like Midtown and whose surrounding few tens of square kilometers look like Paris, with the occasional secondary cluster of skyscrapers at high-demand nodes; let’s call this city “Tokyo.”

Residential development has to keep up as well. A city region that has a strong private economy but doesn’t build enough housing for it will end up with capped production. Normally it’s the lowest-end jobs that get exported. However, two problems make it more than a marginal reduction in production. First, expensive cities have political pressure to allocate apartments by non-market processes like rent control, keeping less productive but politically favored people; a large gap between market rent and construction costs creates plenty of surplus to extract, and a mass exodus of firms from cities like San Francisco in such a situation starts from thee least profitable ones, and by the time it affects the most profitable on, the system is entrenched. And second, breaking a firm’s chain between high-end headquarters jobs in a rich city center and lower-end subsidiary jobs elsewhere reduces firmwide productivity, since many connections have to be remote; Google has problems with all-remote teams and tries to center teams in the Bay Area when it gets too unwieldy.

For one example of a city that does everything right, look at Seoul. It has low construction costs, around $150 million per kilometer for urban subways. Thanks to its low costs and huge size, it keeps building up its system even though it already has one of the largest systems in the world, probably third in ridership after Tokyo and Osaka when one includes all commuter lines. It also has high density, high-rise CBDs, and fast housing construction; in 2019 the Seoul region built around 10 units per 1,000 people, representing a decline since the mid-2010s, and the state has plans to accelerate construction, especially in the city, to curb rising prices. This is till a better situation than the weak economy and flagging construction in much of Europe, or the NIMBY growth rates of both much of the rest of Europe and the richest American cities.


KWCIMBY, or Kowloon Walled City in My Backyard, is a refrain used by some YIMBYs to make it clear that we favor high density and not the missing middle self-compromise. This is not about the literal KWC, which was poor and hideously overcrowded – the floor area ratio from photos looks like it averaged around 8 counting open space, so the density meant it had maybe 6.5 square meters of built-up space per capita. Rather, it’s about the concept of going as high as possible, using higher floor area ratios (the Upper East and West Sides of New York have 12 residential FAR on the avenues) and generous first-world urban living arrangements to create high urban density. This post is about how it might look.

One possible built form is this:

This is 100*100 meter blocks, with 20-meter wide streets; this is not intended to be a city for cars, but at high residential density it’s useful to widen the streets somewhat to provide ample walking and cycling space and to allow very tall buildings while keeping the building height-to-street width ratio reasonable. The buildings are in dark gray, in euroblock form with the courtyards denoted in green.

Internal building layout

The building is 20-meter thick, which is wider than normal for Berlin euroblocks but compensates by not having internal wings, so that the apartments’ area-to-window frontage ratio is about 9 meters, which figure exists in Berlin and Paris. The inner corners feature elevator lobbies, depicted as 10*10 meters, but they can safely be made smaller. Let’s Go LA’s post about high-rise floorplates in Los Angeles, Seattle, and Vancouver shows some examples of elevator lobbies with scissor stairs and some extra corridor space at 63 m^2, and here scissor stairs aren’t needed for fire safety because each of the corners is redundant with the other three.

The footprint of the built-up area is 4,800 m^2. Of that, 722 are circulation space, or 15%; this is not amazing, and it’s possible to do better by having somewhat narrower corridors than 2 meters and somewhat smaller elevator lobbies, reaching about 90% efficiency instead of 85%. If the lobbies remain 10*10, they may include additional functions, such as trash rooms with chutes, or maybe laundry rooms in cities where it’s not normal for people to own washing machines.

The apartment floor plates are forced to be rectangular and not terribly interesting, with rooms opening to windows. My presumption is that each window space is 2.5 meters wide, so a bedroom or an office occupies one window, a living room one to two windows, and unusually large bedroom two. Kitchens can take a full window or be in an open plan with the living room. Bathrooms don’t normally get window space, and the depth of the apartment is such that every bedroom can have an attached bathroom.

An austere apartment is around one window per person, or around 22.5 m^2 per person; a spacious one is around two per person if it’s a family, or 45 m^2 per person, or even three for a single person who wants a guestroom. 45 is normal by Northern European standards and if anything on the low side by American ones, but it’s in practice degressive in household size and American NIMBYism is such that families rarely live in big cities, a household in which half the people are children and therefore do not work not really being able to compete for scarce urban land with a household in which all members work. If there’s abundant space, then middle-class families will take 8-window, 180 m^2 apartments in such buildings, and working-class ones will take 4-window apartments.

So what’s the density?

The courtyard is fully enclosed, so the limit to how much sunlight the bottom apartments get is the ratio of the building’s height to the courtyard width, which is 40 m. In Berlin and Paris one finds many euroblocks with wings such that the ratio of the height to the courtyard width is around 1.8, and a fair number in the 2-2.5 range. Our building can have 25-30 floors, or a height of 75-90 meters, while respecting this ratio. This is a building height-to-street width ratio of about 4, which is not common in Paris and Berlin (I see a bunch of 2 but not 4), but does exist in central residential areas in Tokyo and I think also Taipei, and in commercial ones in New York and London.

25 floors times a little more than 4,000 net m^2 per floor is 102,000 net m^2. If it’s 30 floors, make it 122,000. Figure exactly 45 net m^2 per person, with the more austere floor plans canceling out with vacant apartments, with empty nester apartments, and with three-window, 67.5 m^2 singles. This is 2,265 people per hectare at 25 floors, or 2,718 at 30 floors. Per km^2, this is 226,500, or 271,800 at 30 floors.

The vast majority of built-up space is residential, but with buildings this tall, the ground floor is presumably retail. One trick that can be done is to have retail, such as a supermarket, occupy the entire 80*80 block not including the street, and then put the courtyard on the roof of the supermarket, allowing one or two more residential floors.

A percentage of the buildings is entirely non-residential, such as schools, hospitals, office buildings, and emergency services. Schools are, in British standards, 5.13 m^2/primary student (p. 9), 7.81 m^2/secondary student (p. 10), and 9.28 m^2/16+ student (p. 11), all assuming maximum school size. Schools can be bigger than the maximum assumed in the UK – New York’s Specialized High Schools are each around 1,000 students per grade, and Singapore’s secondary schools and junior colleges have around 700-800 per grade. A 12-story euroblock will fit 6 grades generously at 1,000 students per grade, which is compatible with a base population of around 80,000 at equilibrium, so a square kilometer with 200,000 people needs 2.5 primary and 2.5 secondary schools, or 5 out of 100 blocks used for non-residential purposes. This is the biggest nonresidential, noncommercial use, I believe – everything else is probably 1 building out of 100 each, and maybe a handful of blocks can be parks, with a total of 10 blocks in 100 neither residential nor commercial.

Non-euroblock forms

Instead of euroblocks, it’s possible to use building forms without internal courtyards. For example, one can break each 100*100 block into 50*50 blocks, still with 20 m street width, giving 30*30 buildings:

Instead of 4,800 m^2 of built-up area per hectare one gets 3,600, but the floor plate efficiency, again stolen from the standards in the Let’s Go LA post (this time, with scissor stairs), is more than 90%, and the building sizes are completely standard for high-rises in Tel Aviv or Vancouver. With no internal courtyards, one can get 30 floors or so, which at 45 m^2/person is 222,900 people/residential km^2, or maybe a little less because of ground floor retail.

There’s also the modernist form of linear buildings, typical of communist-era blocks in Eastern Europe, and some postwar public housing projects in the Western Bloc, especially France (but the United States preferred cruciform buildings).

The street width in the direction parallel to the building widens, which in cities that retrofit such forms can be seen as generous setbacks, allowing the same amount of light to reach the lower floors with taller buildings. The overall built up area is 3,200 m^2 per floor, of which 2,864 is net. If we keep to a 4-to-1 height-to-street width ratio we can reach 40 floors now, which is 254,600 people per residential km^2.

The streets in this case can be set up to create long parallel blocks, or to do the opposite, alternating the orientation of the buildings to break the wind. And of course, all building forms can be mixed, so one block is a euroblock, the next is four 30*30 buildings, the one after is two linear blocks, and perhaps the one next to that is two 30*30s and a linear block.

Where is this appropriate?

Construction costs for buildings are not entirely linear in building height. The reason one would build 30-story buildings one after the other rather than single-story houses is that the area has high demand. So your town of 200,000 people has no chance of fitting in one km^2 with such buildings – nobody needs such a built form, even if there are no cars, because if there are no cars then every street is automatically a bike lane and then the town’s range is maybe 10 kilometers and it doesn’t really need multistory apartments except maybe right near the center.

So this is a way of organizing large cities. The use of buildings that are not just tall but also big reinforces the size of the city as well – a city of 100 buildings is a city with severe monopoly problems among developers and landlords, whereas one with 5,000 is one where people are upset at large developers but there is meaningful competition for tenants. Cities that are large but not hug would presumably use the 30*30 building form in preference to the euroblock just because it can be done by smaller developers.

In practice, it’s also a way of organizing large, growing cities, or cities that will grow if development is liberalized. One doesn’t easily replace heterogeneous blocks with big buildings without a lot of demand. Tel Aviv and Vancouver have 30*30 skyscrapers because they are medium-size, high-demand cities, so any site near city center with a few small buildings can be redeveloped; of note, neither uses this building form much outside city center, except perhaps at transit-oriented development sites around designated town centers like Metrotown.

So the isotropic picture at the beginning of the post is an abstraction. In practice, there are always gradients in density, and that’s fine. Some areas get 40-story buildings, other gets smaller ones, or no redevelopment at all; that’s why, even in environments with liberalized zoning like Tokyo and Seoul, neighborhood-scale zones do not reach 200,000/km^2 at developed-world crowding levels. KWC was a unique situation, a tiny no man’s land, and even though Hong Kong is the developed world’s overcrowding capital and has tall buildings to boot, its built-up density has not recurred.

That said, KWCIMBY building forms remain valuable for urban design. City centers genuinely need more development, and while the very center of the city should mostly have offices, one doesn’t need to go too far to get to areas that are mostly residential and mostly very desirable. Tall, densely spaced buildings reaching 200,000 people/km^2 would facilitate comfortable living in the post-car city, and it’s useful to plan for them in the near future.

Is Remote Work Viable?

No, not in the long run.

This has big implications for cities in the future, because it means firms will want to cluster more near production amenities – that is, other high-productivity firms. A city like New York manifestly has very weak consumption amenities, because in the spring it proved that its government is dangerously incompetent in a crisis – but its production amenities are likely to grow, because more firms will want to locate there and in other big, rich cities.

Remote work and the tech industry

The tech industry has long been familiar with remote work. The big multinationals have offices worldwide and some teams are remote, and some small firms are even all-remote. Much of this is an adaptation to the industry’s inability to bring everyone to San Francisco and Silicon Valley, where housing is too expensive and work visas are scarce. This has led to a big internal debate about the future of work; for decades now there have been predictions that the Internet would facilitate remote work and therefore reduce the need for cities to exist as office work centers.

The industry also reacted to corona slightly faster than the rest of the Western world. I’m not sure why – usually the American tech industry sneers at anything that comes out of Asia. But for whatever reason, Google sent its workers home in early March, and has been on work-from-home since, as have the other tech employers.

However, this was always intended to be a temporary arrangement. Workers were told to go back to the office when the crisis ended, at a date that keeps being pushed back and is now September 2021. Moreover, it appears that the industry wants to consolidate rather than disperse: Google, Amazon, Facebook, and Apple are all buying up office space in Manhattan, planning to add 22,000 jobs there. This is not San Francisco, but it’s the closest thing: New York is the United States’ second richest metropolitan region, and (I believe) the second biggest tech job center, with New York hosting the largest non-Bay Area Google office.

The problems with remote work

I have asked a number of people to talk to me about their experience with working from home. All are American professionals; this is far and away the easiest socioeconomic class to do an ethnography of. At no point did anyone ever tell me that everyone in their office is as productive working from home as they had been working as a team at the office. The work from home productivity loss is real; it does not affect everyone, but it affects enough people to be noticeable.

Specific problems I was told include,

  • Corona specifically is a very stressful event, so everyone is on edge and less productive than the usual.
  • Without continuous office work, it’s harder to onboard junior workers, even when senior workers are fine at home. Junior workers also lose the benefits of close mentoring.
  • Parents with children have to take on additional care duties, and without a stay-at-home parent this is difficult.
  • I believe in one case I was told the opposite of the above – that given that children are at home, it’s easier for parents than for non-parents.
  • At least per the CEO of United, who is obviously biased on this, firms perceive in-person sales to be more successful than virtual ones. In general, I’ve been told that work facing clients is less productive when it’s virtual and law firms can work remotely in the short run with their existing client base but in the long run they need the office.

The standard production theory, articulated for example by Alain Bertaud, is that working from home is less productive because there are no spontaneous interactions, and this seems true although I don’t recall anyone telling me this exact thing literally, but very similar problems are apparent.

What does this mean for cities?

Before corona, it was not always clear whether advances in telecommunications would make remote work viable. It increasingly looks like the answer is no, and therefore the most productive firms are likely to center around their usual clusters, just as the tech firms are buying up Manhattan office space. The upshot, then, is that high-cost, high-productivity city centers are likely to see more commercial demand in the medium and long runs.

One model that I’ve heard from multiple sources is mixed, for example 2-4 days a week at the office, 1-3 days remote. If this happens, then it will mean that people commute fewer days. This has opposite effects on office and residential geography: fewer commutes mean it’s more acceptable to live farther out and have longer work trips on work-at-office days, which encourages either suburbanization or hopping over to the next city over; for the exact same reason, it’s also more acceptable to site offices in areas with more traffic congestion, that is city center.

What does this mean for public transportation?

More urban job concentration universally requires better public transportation, since rapid transit is far and away the most efficient mode of transportation measured in capacity provided per unit of right-of-way width. However, the details are subtle. Most importantly, the American upper middle class mostly does not work 9 to 5 at the most productive firms. The tech industry tends toward shifted hours, especially on the East Coast in order to overlap Silicon Valley better, and even for the same reason in Israel. So the impact of more tech employment in Midtown is not that New York desperately needs more subway capacity, but rather that it needs to broaden the peak to last until 10 in the morning rather than 9. This conclusion does not depend much on whether workers show up at the office every day or only 3-4 days a week, because 60-80% of rush hour traffic still requires peak or near-peak train throughput.

There were many Americans who, back when corona seemed to be first and foremost a New York problem, predicted the end of cities, or the conversion of cities to spaces of consumption. Joel Kotkin even blamed New York’s density for corona and praised Los Angeles’s sprawl; now that Los Angeles is running out of hospital beds, nobody in the US blames density anymore. (One could also point out Seoul and Tokyo’s density, but not even 460,000 deaths and counting will make Americans say “our country needs to be more like other countries.”)

But this is not looking to happen. The most productive firms in the US are urbanizing – and those are the most productive firms in the world; it averages out with horrific American public-sector inefficiency to about the same GDP per hour as in Germany. And this means that going forward, the richest, most productive, and most expensive cities will remain spaces of high-end production, and will need to build sufficient numbers of office towers and residences and improve public transportation infrastructure to accommodate.

Quick Note: Consumption and Production Theories of Berlin

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

The situation in Berlin

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

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

Berlin’s production amenities

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


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

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

The capital

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

Good infrastructure

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

Consumption theory and the counterculture

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

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

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

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

What Suburban Poverty?

Myth: American cities have undergone inversion, in which poorer people are more suburban than richer people.

Reality: at least on the level of people commuting to city center, wages generally rise with commute distance. In particular, the phenomenon of supercommuters – people traveling very long distances to work – is a middle- and high-income experience more than a low-income one. This is true even in Los Angeles, a Sunbelt city with more of a drive-until-you-qualify history than the Northeastern cities. The only exception among the largest US cities is San Francisco, and there too, the poorest distance is 5-10 km out of the Financial District.

All data in this post comes from OnTheMap and is as of 2017, the latest year for which there is data. The methodology is to define a central business district, generally a looser one than in past post but still much smaller than the entirety of the city, and look at people who work in it and live within annuli of increasing radius from a specific central point within the CBD. OnTheMap puts jobs into three income buckets, the boundary points being $1,250 and $3,333 per month; we look at the proportion of jobs in the highest category.

I report the annuli in kilometers, but technically they’re in multiples of 3.11 miles, which is very close to 5 km.

CityNew YorkLos AngelesChicagoWashingtonSan FranciscoBoston
CBD3rd, 60th, 9th, 30thI-10, I-110, riverCongress, I-90, Grand6th, R, river, EBroadway, Van Ness, 101, 16thI-90, water, Arlington
PointGrand Central7th/Metro CenterState/MadisonFarragutMarket/2ndDowntown Crossing
40k+ %68.7%68.8%70.4%69.8%73.2%71.7%
0-5 km211,91022,55767,34856,57886,84541,912
40k+ %79.8%44.6%84%75.1%76.6%70.5%
5-10 km205,21538,98691,33256,15467,06352,499
40k+ %63.6%53.2%70.1%61.5%68.3%64.3%
10-15 km172,11742,39188,60438,23349,11130,619
40k+ %51.9%65.1%58.8%66.2%73.6%73.3%
15-20 km101,54341,22967,62023,58935,69220,444
40k+ %62%71.3%67.3%69.8%74.5%76.8%
20-30 km92,87153,80968,57127,92140,17029,271
40k+ %74.4%75.6%73.5%75.8%76.9%79%
30-40 km61,23633,05149,37415,56833,39517,511
40k+ %81.1%77.6%76.1%78%80.1%77.8%
40-50 km37,93117,56141,7458,40320,50912,738
40k+ %82.1%81%78.7%82%82.4%78.7%
50-60 km26,74613,85325,8723,34615,9819,321
40k+ %81.3%82.3%74.9%76.7%78.7%76.9%
60-70 km21,8608,56114,9402,59614,6826,101
40k+ %80.3%83.6%74.5%76.9%73.3%71.5%
70-80 km14,0077,7205,4711,4449,1514,757
40k+ %77.8%79.7%72.4%79.3%69.8%74.2%

In all six metro areas above except Los Angeles, the income in the innermost 5-km circle is higher than in the 5-10 km annulus. In Chicago that inner radius is in fact the wealthiest, but in Boston it’s below average, and in New York, Washington, and San Francisco it is poorer than wide swaths of suburbia. There is always a large region of poverty in an urban radius, which is roughly the inner 15 km in Los Angeles, the 5-20 km annulus in New York, the 10-15 km radius in Chicago, and so on.

This of course does not take directionality into account. In Chicago, it is especially important – to the north, there is wealth at all radii, and to the south, there is mostly poverty. In contrast, in New York directionality is less important, and it is in a way the purest example of the poverty donut model, in which the center is rich, the suburbs are rich, and the in-between neighborhoods are poor, without wedges that form favored quarters or wedges that form ill-favored quarters.

The importance of this is that because the inner and outer limits of the poverty donut are slowly moving outward, there is talk of suburbanization of poverty – or, rather, there was in the decade leading up to corona, but I suspect it will return once mass vaccination happens. However, even now, American cities are not Paris or Stockholm, where wealth mostly decreases as distance from the center increases, even though both cities have intense directionality (rich northeast, poor south and west in Stockholm, and the exact opposite in Paris). The poorest place remains the inner city, just beyond the near-downtown zone at what I would call biking range from city center jobs if any American city had even semi-decent biking infrastructure.

This contrasts with various schemes to subsidize suburbs that assume poverty has already suburbanized. Massachusetts, where even in the inner 5 km radius the $40,000+ share is below average, has a concept called Gateway Cities, defined to mean roughly “low- and lower-middle-income cities that aren’t Boston.” Of those, about one, Chelsea, is inner-urban, while the others include Springfield and various ex-industrial cities that are generally no poorer than Boston and lie amidst suburban wealth, like Lowell and Haverhill. Based on the idea that Massachusetts poverty is in the Gateway Cities and not in Boston itself, it justifies vast place-based subsidies that mostly go to people who are decently well-off while Dorchester has to beg for slightly better public transportation to Downtown Boston.

In New York, one likewise hears more about the poverty of Far Rockaway than about that of Harlem. There’s this widespread belief that Harlem is no longer poor, that it’s fully gentrified because there’s one bagel shop on 116th Street that caters to a mostly white middle-class clientele. This is related to the stereotype of the Real New Yorker, weaponized so that the cop or the construction worker who is a third-generation New Yorker and lives at the outermost edge of the city is an inherently more moral person than the Manhattanite or the immigrant and is the very definition of the working class while earning $90,000 a year. This goes double if this Real New Yorker lives on Long Island, usually with some catechism about how the city is too expensive even though the suburbs are about equally costly. The one place-based policy that would benefit the city, having the state integrate its schools with those of the generally better-resourced suburbs, is unthinkable.

It’s notable that this discourse that overrates how poor American suburbia is comes exclusively from people who tend to sympathize with the poor. People with Thatcherist attitudes toward the poor abound in the United States, and tend to correctly believe that the inner city is poorer than the suburbs, and if anything to overrate the extent of urban poverty. In either case, the conclusion groups of Americans reach is that the government must subsidize the suburbs further; all else is just motivated reasoning.

In reality, if one has the Thatcherist or Old Tory moralistic attitude that poverty is a personal failure then, with reservations, one should continue believing the large American city is inherently immoral. But if one has the attitude that poverty is a social failure that is solvable with social programs, then one must realize that there is more of this in central cities than in their suburbs, even faraway suburbs that are called drive-until-you-qualify because they are slightly poorer than some other suburbs, and therefore if anti-poverty programs must be place-based then they should be urban.

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.


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.


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

What is a tram-train?

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

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

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

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

Tram-trains and regional rail

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

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

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

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

Where is a tram-train appropriate?

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

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

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

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

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

Different models of urban geography

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

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

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

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

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

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

Israel and tram-trains

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

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

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

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

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

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

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

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

Job Sprawl as Deurbanization

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

Cities as job markets

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

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

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

Aaron Renn’s bifurcation

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

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

Is this polycentricity?

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

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

The public transit solution

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

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

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

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

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

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

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