Category: Urban Design

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.

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.

Pedestrianizing Streets in New York

I was asked a few months ago about priorities for street pedestrianization in New York. This issue grew in importance during the peak of the corona lockdown, when New Yorkers believed the incorrect theory of subway contagion and asked for more bike and pedestrian support on the street. But it’s now flared again as Mayor de Blasio announced the cancellation of Summer Streets, a program that cordons off a few streets, such a the roads around Grand Central, for pedestrian and bike traffic. Even though the routes are outdoors, the city is canceling them, citing the virus as the reason even though there is very little outdoor infection.

But more broadly, the question of pedestrianization is not about Summer Streets, which is an annual event that happens once and then for the rest of the year the streets revert to car usage. It’s about something bigger, like the permanent Times Square and Herald Square pedestrianization.

In general, pedestrianization of city centers is a good thing. This can be done light, as when cities take lanes off of roadways to expand bike lanes and sidewalks, or heavy, as when an entire street loses car access and becomes exclusive to pedestrians and bikes. The light approach should ideally be done everywhere, to reduce car traffic and make it viable to bike; cycling in New York is more dangerous than in Paris and Berlin (let alone Amsterdam and Copenhagen) since there are too few separated bike lanes and they are not contiguous and since there is heavy car traffic.

The heavy approach should be used when feasible, but short of banning cars cannot be done everywhere. The main obstacle is that in some places a critical mass of consumers access retail by car, so that pedestrianization means drivers will go elsewhere and the region will suffer; this happened with 1970s-era efforts in smaller American cities like Buffalo, and led to skepticism about the Bloomberg-era Times Square pedestrianization until it was completed and showcased success. Of course, Midtown Manhattan is rich in people who access retail by non-auto modes, but it’s not the only such place.

Another potential problem is delivery access. This is in flux, because drone delivery and automation stand to simplify local deliveries, using sidewalk robots at pedestrian scale. If delivery is automated then large trucks no longer offer much benefit (they’re not any faster than a bicycle in a congested city). But under current technology, some delivery access is needed. In cities with alleys the main street can be pedestrianized with bollards while the alleys can be preserved for vehicular access, but New York has about three alleys, which are used in film production more than anything because they connote urban grit.

Taking all of this together, the best places for pedestrianization are,

  1. City centers and near-center areas. In New York, this is the entirety of Manhattan south of Central Park plus Downtown Brooklyn and Long Island City. There, the car mode share is so low that there is no risk of mass abandonment of destinations that are too hard to reach by car.
  2. Non-residential areas. The reason is that it’s easier to permit truck deliveries at night if there are no neighbors who would object to the noise.
  3. Narrow streets with plenty of commerce. They’re not very useful for drivers anyway, because they get congested easily. If there are deliveries, they can be done in off-hours. Of note, traffic calming on wider streets is still useful for reducing pollution and other ills of mass automobile use, but it’s usually better to use light rather than heavy traffic reduction, that is road diets rather than full pedestrianization.
  4. Streets with easy alternatives for cars, for example if the street spacing is dense. In Manhattan, this means it’s better to pedestrianize streets than avenues.
  5. Streets that are not useful for buses. Pedestrianized city center streets in Europe are almost never transit malls, and the ones I’m familiar with have trams and not buses, e.g. in Nice.

Taking this all together, some useful examples of where to pedestrianize in New York would be,

  1. Most of Lower Manhattan. There are no residents, there is heavy commerce, there is very heavy foot traffic at rush hour, and there are enough alternatives that 24/7 pedestrianization is plausible on many streets and nighttime deliveries are on the rest.
  2. Some of the side streets of Downtown Brooklyn and Long Island City. This is dicier than Manhattan – the mode share in those areas as job centers is far below Manhattan’s. A mid-2000s report I can no longer find claimed 50% for Downtown Brooklyn and 30% for LIC, but I suspect both numbers are up, especially LIC’s; Manhattan’s is 67%, with only 15% car. So there’s some risk, and it’s important to pick streets with easy alternatives. Fulton Mall seems like a success, so presumably expansions can start there and look at good connections.
  3. St. Mark’s. It’s useless for any through-driving; there’s a bus but its ridership is 1,616 per weekday as of 2018, i.e. a rounding error and a prime candidate for elimination in a bus redesign. There’s so much commerce most buildings have two floors of retail, and the sidewalk gets crowded.
  4. Certain Midtown side streets with a lot of commerce (that’s most of them) and no buses or buses with trivial ridership (also most of them). One-way streets that have subway stations, like 50th and 53rd, are especially attractive for pedestrianization. Two-way streets, again, are valuable targets for road diets or even transit malls (though probably not in Midtown – the only east-west Manhattan-south-of-59th-Street bus route that screams “turn me into a transit mall” is 14th Street).

School Transit-Oriented Development

Transit-oriented development, or TOD, means building more stuff in places with good access to public transportation, typically the immediate vicinity of a train station. This way people have more convenient access to transit and are encouraged to take it because they live or work near the train, or ideally both. In practice, American implementations heavily focus on residential TOD, and secondarily on commercial TOD, the latter focusing more on office than retail. I covered some retail issues here; in this post, I’m going to look at a completely different form of TOD, namely public-sector institutions that government at various levels can choose the location of by fiat. These includes schools, government offices, and cultural institutions like museums. Of these, the most important are schools, since a huge share of the population consists of schoolchildren, who need convenient transportation to class.

This principle here is that the state or the city can site public schools where it wants, whether it’s by diktat or by inducements through funding for school construction. This occurs even in situations with a great deal of autonomy: American suburban schools are autocephalous, but still receive state funding for school construction, and if anything that incentivizes moving to new suburban campuses inaccessible by public transit. Other cultural institutes are usually less autonomous and more strapped for cash, and getting them to move to where it’s easier for people to access them without a car should be easier.

School siting: central cities

Urban schools tend to spread all over the city. There are more schools in denser and younger neighborhoods; there also are more high-end schools (Gymnasiums, etc.) in richer neighborhoods. But overall, there isn’t much clustering. For example, here is what I get when Googling both Gymnasiums in Berlin:

There are many Gymnasiums in rich areas like Wilmersdorf and few in poor areas (the map shows one in Neukölln and none in Gesundbrunnen and Wedding, although a few that aren’t shown at this zoom level do exist). But overall, the school locations are not especially rail-oriented. They’re strewn all over the middle-class parts of the city, even though most students do not live close enough to walk. Only the most specialized of the elite schools is in city center, the French school.

The situation in New York is similar to that of Berlin – the schools in the city are all over. This is despite the fact that there’s extensive school choice at the high school level, so that students typically take the subway and bus network over long distances. New York’s school stratification is not the same as Berlin’s – its Specialized High Schools serve the top 3% of city population, Germany’s Gymnasiums serve maybe 30% – but there, too, schools that explicitly aim to draw from all over the city are located all over the city. Only the most elite of New York’s schools, Stuyvesant, is in the central business district, namely in Lower Manhattan; the second and third most elite, Bronx Science and Brooklyn Tech, are just outside Downtown Brooklyn and in the North Bronx, respectively. A huge fraction of Bronx Science’s student population commutes from feeder neighborhoods like Flushing, Sunset Park, Chinatown, Jackson Heights, and the Upper West Side, and has to wake up early in the morning for an hour-long commute.

If schools are not just for very local neighborhood children, then they should not be isotropic, or even middle-class-isotropic as in Berlin. They should be in areas that are easily accessible by the city’s rapid transit network, on the theory that the time of children, too, is valuable, and replacing an hour-long commute with a half-hour one has noticeable benefits to child welfare and educational outcomes.

Urban school nodes

So to improve transit access to school in transit cities, it’s useful to get schools to move to be closer to key nodes on the rail network. City center may be too expensive – the highest and best use of land around Times Square or Pariser Platz is not a school. But there are other useful nodes.

The first class of good locations is central and near-center areas that don’t have huge business demand. In New York, Lower Manhattan and Downtown Brooklyn both qualify – business prefers Midtown. In Berlin, there are a lot of areas in Mitte that don’t have the development intensity of Potsdamer Platz, and to some extent the French school picked such an area, on the margin of Mitte.

The second is key connection points on the rail network that are not in the center. Berlin is rich in such connections thanks to the Ring. To some extent there are a bunch of schools close to Ringbahn stations, but this isn’t perfect, and for example the Europasportspark shown on the map is between two Ringbahn stations, at one of the few arterial roads through the Ring that doesn’t have an S-Bahn station. In New York, there is no ring, so connections are more sporadic; desirable nodes may include Queensborough Plaza, Metropolitan/Lorimer in Williamsburg, and East New York.

East New York supplies an example of the third class: an area that is rich in transit connections but is commercially undesirable because the population is poor. (The Berlin equivalent is Gesundbrunnen – non-German readers would be astounded by the bile Germans I know, even leftists who vote for anti-racist politicians, heap on U8 and on Gesundbrunnen and Neukölln.) Since everyone goes to school, even working-class children, it is valuable to site schools and other cultural amenities in such areas for easy accessibility.

One important caveat is that freeways, which make office and retail more attractive, have the opposite effect on schools. Air pollution makes learning more difficult, and children do not own cars and thus do not benefit from the convenience offered by the car. If rail lines are near freeways, then schools should be set somewhat away, on the principle that the extra 5-minute walk is worth the gain in health from not sitting hours in a polluted environment.

The suburbs

Outside the cities, the place for schools is the same as that for local retail and offices: the town center, with a regional rail station offering frequent access by train and timed connections by bus. Even when the student population is local, as it is in American suburbs, the density is too low for people to walk, forcing some kind of mechanized transportation. For this, the school bus is a poor option – it is capital-intensive, requiring what is in effect a second bus system, one that is as useless for non-students as the regular buses are for students if the school is far away from the local transit network.

Instead, a central school location means that the suburban bus network, oriented around city center, is useful for students. It increases transportation efficiency rather than decreasing it – there is no duplication of service, and the school peaks don’t usually coincide with other travel peaks, like the office worker peak and the retail worker peak. The bus network, designed around a 15- or 30-minute clockface schedule, also means that students can stay in longer, if they have on-campus club activity or if they have things to do in the town center, such as going shopping.

In some distant suburbs the school peak, arriving around 8 in the morning, may be the same as the peak for office workers who take the bus to the train to go to the central city. This isn’t necessarily a bad thing – for parents who insist on driving, this makes it easier to drop off children on the way to work. If this turns out to create real congestion on the bus, then the solution is to move school start time later, to 9 or so.

It’s crucial to use state power to effect this change when possible. For example, Massachusetts funds school construction through state funds but not renovation, which has encouraged schools to move to new campuses, generally in harder-to-reach areas. Fitchburg’s high school used to be in city center but recently moved to a suburban location close to nothing. Even in environments with a lot of local autonomy, the state should fund school construction in more central areas.

Density and Subway Stop Spacing

Normally, the best interstation distance between subway or bus stops does not depend on population density. To resurrect past models, higher overall density means that there are more people near a potential transit stop, but also that there are more people on the train going through it, so overall it doesn’t influence the decision of whether the stop should be included or deleted. Relative density matters, i.e. there should be more stops in areas that along a line have higher density, for example city centers with high commercial density, but absolute density does not. However, there is one exception to the rule that absolute density does not matter, coming from line spacing and transfer placement. This can potentially help explain why Paris has such tight stop spacing on the Métro and why New York has such tight stop spacing on the local subway lines.

Stop spacing and line spacing

The spacing between transit stops interacts with that between transit lines. The reason is that public transportation works as a combined network, which requires every intersection between two lines to have a transfer. This isn’t always achieved in practice, though Paris has just one missed connection on the Métro (not the RER), M5/M14 near Bastille; New York has dozens, possibly as many as all other cities combined, but the lines built before 1930 only have one or two, the 3/L in East New York and maybe the 1/4-5 around South Ferry.

The upshot is that the optimal stop spacing depends on the line spacing. If the line spacing is tight – say this is Midtown Manhattan and there is a subway line underneath Lex/Park, Broadway, 6th, 7th, and 8th – then crossing lines have to have tight stop spacing in order to connect to all of these parallel lines. In the other direction, there were important streetcars on so many important cross-streets that it was desirable to intersect most or ideally all of them with transfers. With so many streetcar lines extending well past Midtown, it is not too surprising that there had to be frequent subway stops.

So why would denser cities have tighter line spacing?

Line spacing and density

The intuitive relationship between line spacing and density is that denser cities need more capacity, which requires them to build more rail lines.

To see this a bit more formally, think of an idealized city on a grid. Let’s say blocks are 100*100 meters, and the planners can figure out the target density in advance when designing the subway network. If the city is very compact, then the subway could even be a grid, at least locally. But now if we expect a low-density city, say 16 houses per block, then the subway grid spacing should be wide, since there isn’t going to be much traffic justifying many lines. As the city densifies, more subway is justifiable: go up to missing middle, which is around 30-40 apartments per block; then to the Old North of Tel Aviv, which would be around 80; then to a mid-rise euroblock, which is maybe 30-40 per floor and 150-200 per block; then finally a high-rise with maybe 500-1,000 apartments.

Each time we go up the density scale, we justify more subway. This isn’t linear – an area that fills 500 apartments per block, which is maybe 100,000 people per km^2, does not get 20 times the investment of an area on the dense side of single-family with 16 houses per block and 5,000 people per km^2. Higher density justifies intensification of service, with bigger and more frequent trains, as well as more crowding. With more subway lines, there are more opportunities for lines to intersect, leading to more frequent stop spacing.

Even if the first subway lines are not planned with big systems in mind, which New York’s wasn’t, the idea of connections to streetcar lines was historically important. A stop every 10 blocks, or 800 meters, was not considered on the local lines in New York early on; however, stops could be every 5 blocks or every 7, depending on the spacing of the major crosstown streets.

Dense blobs and linear density

Line spacing is important to stop spacing not on parallel lines, but crossing lines. If a bunch of lines go north-south close to one another, this by itself says little about the optimal spacing on north-south lines, but enforces tight spacing on east-west lines.

This means that high density encourages tight stop spacing when it is continuous in a two-dimensional area and not just a line. If large tracts of the city are very dense, then this provides justification for building a grid of subway, since the crosstown direction is likely to fill as well; in New York, 125th Street is a good candidate for continuing Second Avenue Subway Phase 2 as a crosstown line for this reason.

In contrast, if dense development follows a linear corridor, then there isn’t much justification for intense crosstown service. If there’s just one radial line, then the issue of line spacing is moot. Even if there are two closely parallel radial lines in the same area, a relatively linear development pattern means there’s no need for crosstown subways, since the two lines are within walking distance of each other. The radial urban and suburban rail networks of Tokyo and Seoul do not have narrow interstations, nor do they have much crosstown suburb-to-suburb service: density is high but follows linear corridors along rapid transit. Dense development in a finger plan does not justify much crosstown service, because there are big low-density gaps, and suburb-to-suburb traffic is usually served efficiently by trips on radial lines with a transfer in city center.