Austerity is Inefficient

Working on an emergency timetable for regional rail has made it clear how an environment of austerity requires tradeoffs that reduce efficiency. I already talked about how the Swiss electronics before concrete slogan is not about not spending money but about spending a fixed amount of money intelligently; but now I have a concrete example for how optimizing organization runs into difficulties when there is no investment in either electronics or concrete. It’s still possible to create value out of such a system, but there will be seams, and fixing the seams requires some money.

Boston regional rail

The background to the Boston regional rail schedule is that corona destroyed ridership. In December of 2020, the counts showed ridership was down by about an order of magnitude over pre-crisis levels. American commuter rail is largely a vehicle for suburban white-collar commuters who work in city center 9 to 5; the busiest line in the Boston area, the Providence Line, ran 4 trains per hour at rush hour in the peak direction but had 2- and 2.5-hour service gaps in the reverse-peak and in midday and on weekends. Right now, the system is on a reduced emergency timetable, generally with 2-hour intervals, and the trains are empty.

But as Americans get vaccinated there are plans to restore some service. How much service is to run is up in the air, as is how it’s to be structured. Those plans may include flattening the peak and going to a clockface schedule, aiming to start moving the system away from traditional peak-focused timetables toward all-day service, albeit not at amazing frequency due to budget limits.

The plan I’ve been involved with is to figure out how to give most lines hourly service; a few low-ridership lines may be pruned, and the innermost lines, like Fairmount, get extra service, getting more frequency than they had before. The reasoning is that the frequency that counts as freedom is inversely proportional to trip length – shorter trips need more frequency and shorter headways, so even in an environment of austerity, the Fairmount Line should get a train every 15 or 20 minutes.

Optimization

In an environment of austerity, every resource counts. We were discussing individual trains, trying to figure out what the best use for the 30th, the 35th, the 40th trainset to run in regular service is. In all cases, the point is to maximize the time a train spends moving and minimize the time it spends collecting dust at a terminal. However, this leads to conflict among the following competing constraints:

  • At outer terminals like Worcester and Lowell, it is desirable that the train should have a timed transfer with the local buses.
  • At the inner terminals, that is South and North Stations, it is desirable that all trains arrive and depart around the same time (“pulse“), to facilitate diagonal transfers, such as from Fitchburg to Salem or from Worcester to Brockton.
  • Some lines have long single-track segments; the most frustrating is the Worcester Line, which is in theory double-track the entire way but in practice single-track through Newton, where only the nominally-westbound track has platforms.
  • The lines should run hourly, so ideally the one-way trip time should be 50 minutes or possibly 80 minutes, with a 10-minute turnaround.

Unfortunately, it is not possible to satisfy all constraints at once. In an environment with some avenues for investment, it’s possible to double-track single-track bottlenecks, as the MBTA is already planning to do for Newton in the medium run. It’s also possible to speed up lines on the “run as fast as necessary” principle to ensure the trips between knots take an integer or half-integer multiple of the headway; in our higher-investment regional rail plan for Worcester, this is the case, and all transfers and overtakes are tight. However, in a no-investment environment, something has to give. The Worcester Line is 90 minutes end-to-end all-local, and the single-track section is between around 15 and 30 minutes out of South Station, which means it is not possible to conveniently pulse either at South Station with the other commuter lines or at Worcester with the buses. But thankfully, the length of the single-track segment between the crossovers is just barely enough to allow bidirectional local service every 30 minutes.

Discussion

No-investment and low-investment plans are great for highlighting what the most pressing investment needs are. In general Boston needs electrification and high platforms everywhere, as do all other North American commuter lines; it is unfortunate that not a single system has both everywhere, as SEPTA is the only all-electric system and the LIRR (and sort of Metro-North) is the only all-high-platform system. However, more specifically, there are valuable targets for early investment, based on where the seams in the system are.

In the case of integrated timetabling, it’s really useful to be able to make strategic investments, including sometimes in concrete. They should always be based on a publicly-communicated target timetable, in which all the operational constraints are optimized and resolved for the maximum benefit of passengers. For example, in the TransitMatters Regional Rail plan, the timed transfers at the Boston end are dealt with by increasing frequency on the trunk lines to every 15 minutes, at which point the average untimed transfer is about as good as a timed hourly transfer in a 10-minute turnaround; this is based on expected ridership growth as higher frequency and the increase in speed from electrification and high platforms both reduce door-to-door trip times.

The upshot is that austerity is not good for efficiency. Cutting to grow is difficult, because there are always little seams that require money to fix, even at agencies where overall spending is too high rather than too low. Sometimes the timetables are such that a speedup really is needed: Switzerland’s maxim on speed is to run as fast as necessary, not as fast as trains ran 50 years ago with no further improvement. This in turn requires investment – investment that regularly happens when public transportation is run well enough to command public trust.

Cut-and-Cover is Underrated

Subways can be built in two ways: cut-and-cover, and bored tunnel. Cut-and-cover means opening up the street top-down, building the system, and roofing it to restore surface traffic; bored tunnel means opening up one portal and digging horizontally, with less surface disturbance. In the last generation or two there has been a shift toward bored tunnel even in places that used to build cut-and-cover, despite the fact that bored tunnel is the more expensive technique in most cases. Regrettably, people don’t seem to even recognize it as a tradeoff, in which they spend more money to avoid surface disruption – some of our sources have told us that avoiding top-down cut-and-cover is an unalloyed good, a kind of modernity. Even more regrettably, this same thinking is common in much of the developing world, where subways tend to be bored.

What are cut-and-cover and bored tunnel?

Cut-and-cover refers to a family of construction techniques all of which involve top-down tunneling. In New York, one of the sources cited on NYCSubway.org refers to the subway as “a covered trench” rather than a real tunnel. The oldest cut-and-cover subways were dug by hand, but in the last 100 years there have been technological innovations to mechanize some of the work as well as to reduce surface disruption, which is considerable and lasts for a few years. These innovations include the cover-and-cut system invented in 1950s Milan (“Milan method”) and the caisson system used to build T-Centralen in Stockholm. The Milan method sinks piles into the street early and builds retaining walls to allow for truly vertical construction, whereas traditional cut-and-cover must be sloped, which requires a wider street than the tunnel, like the Manhattan avenues or Parisian boulevards but not Milan’s Renaissance streets. The caisson method builds a concrete structure and then lowers it into the ground, which facilitates multistory cut-and-cover structures at transfer stations.

Bored tunnel involves digging just one portal, or sometimes a few to speed up work, and then drilling horizontally. This used to be called a tunneling shield, but the shield has been automated to the point that a small crew, only 8-12 people, are required to supervise it nowadays, and now it is called a tunnel-boring machine, or TBM. This method was first invented in London for the construction of the Thames Tunnel, and has been used for all of the London Underground lines since the first two, as London lacks for wide streets for cut-and-cover work. Most American, European, and East Asian cities have switched to this method in the last generation; thus for example New York started to build Second Avenue Subway in the 1970s cut-and-cover, but the program since the 1990s has always been bored.

The typical method used in the world is really a mix – the tunnels are bored, the stations are cut-and-cover. This is because, while the TBM is capable of building tunnels easily, it cannot build stations. Mining or blasting a station is expensive, and many modern examples run up to $500 million or more, not just in high-cost New York but also in otherwise low-cost Rome. This mixed method involves opening up the street at station sites for 1.5-2 years in Paris, intermediate costs, and disruption only at sites that would benefit from the opening of a station.

How much do these techniques cost?

The cost of a mined station starts at $500 million and goes up. But very few cities mine stations – New York and London do, and very rarely other cities do in constrained historic centers like Rome’s. The typical cost of bored tunnel is much less; the lines for which we have seen a breakdown in costs between tunneling and stations, which are a small fraction of our database, have tunneling costs ranging from around $50 million per km to somewhat more than $100 million per km, not counting systems, overheads, or stations. With everything included, this should be viewed as about $200 million per km; the actual median for subways in our database is about $250 million/km, but it includes expensive lines with mined stations, city center tunnels that can’t easily build cut-and-cover stations, and projects that are unusually bad.

Cut-and-cover is generally cheaper. The only cut-and-cover example in our database from Paris, the Line 13 extension to Courtilles, cost 83M€/km, which is around $130 million/km in today’s money; other Paris Métro extensions from the last 15 years are 50-100% more expensive, and the next tranche is even costlier, as Parisian costs are regrettably increasing. Low-cost cities in Southern Europe bore the majority of their subways, but their suburban subway extensions are often a mix of TBMs and cut-and-cover, which is one of many reasons they have low construction costs and Paris does not.

Bear in mind that the superiority of cut-and-cover to bored tunnel depends on the presence of an at least moderately wide straight street for it to go under. London ran out of such streets after it built the Metropolitan line; the District line was, per Wikipedia, three times as expensive, about $110 million/km in today’s money, because it needed to demolish property in Kensington, already then an expensive neighborhood. New York used bored tunnel to cross under rivers and under the hills of Washington Heights, switching to cut-and-cover elsewhere; readers who have gone to the New York Subway Museum will remember the exhibits about the dangerous work of the sandhogs underwater. However, that bored tunnel was no more expensive in turn-of-the-century London than cut-and-cover was in contemporary Paris and New York does not mean these relative costs persist today. Today, on the sort of streets most cities build subways under, cut-and-cover is cheaper, by a factor that appears to be 1.5-2.

The situation in developing countries

In developing countries, I am not aware of any cut-and-cover, which does not mean there isn’t any, just that in the places I’ve looked most closely, namely India and Thailand, the tunnels seem bored. Of note, both India and Thailand build extensive elevated networks, so their subways are to some extent built where elevated construction is infeasible or undesirable. However, to some extent is doing a lot of work here. The Bangkok MRT goes under Rama IV Road, which is about 35 meters wide, and under Asok, which is 30 meters wide. This is comparable to the Sukhumvit, a 35-meter-wide road that hosts the BTS el. Deep-level construction is not necessary on the main roads of Bangkok.

What of other developing-world cities? Bangkok may be unusual, in that it’s a solidly middle-income city, the dominant capital of a middle-income country with comparable GDP per capita to China. What of genuinely poor cities? At least in the bigger ones, wide boulevards for cut-and-cover are not in shortage. Nairobi has vast roads hosting matatu routes. Lagos has such wide main roads that when I crayoned it I proposed that the main radials be elevated, as the under-construction Blue Line is, to avoid having to tunnel underwater from the mainland to Lagos Island. In most cases, short bored segments may be needed, or else short segments that involve the purchase and demolition of private property, as happened in New York when the city carved Seventh Avenue South and Sixth Avenue through the Village.

I suspect the reason this is not done is that planners believe that TBMs are more modern. The physical TBM is an engineering marvel, and looks like advanced technology, even if what it produces is comparable in quality to what cut-and-cover could do when there are wide roads to tunnel under. Planners in the United States have treated it as a given that it’s better to avoid top-down construction. This isn’t even isomorphic mimicry, in which poor countries improperly imitate rich ones; this is proper imitation of a technique whose use in rich countries too is often in error.

Cut-and-cover is underrated

Instead of tunneling wherever possible, I would urge urban subway planners to look to cut-and-cover more. In poor countries, it can be done with the same labor-intensive techniques that produced $40 million/km subways (in today’s money) in New York and Paris. In rich ones, it can be done with more advanced technology to save labor and keep costs under control. This involves more surface disruption, but this disruption can be mitigated by using the Milan method on roads that are wider than those of the center of Milan, and the ultimate benefit is that a lot more subway can be built.

Pulses (Hoisted from Comments)

Robert Jackel asked me an excellent question in comments: what is a pulse? I’ve talked about timed transfers a lot in the last almost 10 years of this blog, but I never wrote a precise definition. This is a critical tool for every public transportation operation with more than one line, making sure that trains and buses connect with as short a transfer window as possible given other constraints. Moreover, pulse-oriented thinking is to plan capital investment and operations to avoid constraints that make transfers inconvenient.

When are pulses needed?

Passengers perceive the disutility of a minute spent transferring to be more than that of a minute spent on a moving vehicle. This is called the transfer penalty and is usually expressed as a factor, which varies greatly within the literature. In a post from 2011 I quoted a since-linkrotted thesis with pointers to Boston and Houston’s numbers, and in a more recent post I found some additional literature in a larger variety of places, mostly in the US but also the Netherlands. The number 2 is somewhere in the middle, so let’s go with this.

Observe that the transfer penalty measured in minutes and not in a factor is, naturally, larger when service runs less frequently. With a factor of 2, it is on average equal to the headway, which is why it is likely the number is 2 – it represents actual time in the worst case scenario. The upshot is that the value of an untimed transfer is higher the higher the frequency is.

I used the principle of untimed transfers and frequency to explain why small subway networks do not look like small bus networks – they have fewer, more frequent lines. Subway lines that run every 3-4 minutes do not need transfer timing, because the time cost of an untimed transfer is small compared to the likely overall trip time, which is typically in the 15-30 minute range. But the lower the frequency, the more important it is to time transfers. Thus, for example, Berlin times the U6/U7 transfer at Mehringdamm in the evening, when trains run every 10 minutes, but does not do so consistently in the daytime, when they run every 5.

But note: while the value of an untimed transfer is higher at higher frequency, the value of a timed transfer is the same – it is zero-penalty or close to it no matter what. So really, the relative value of timing the transfer decreases as frequency increases. But at the same time, if frequency is higher, then more passengers are riding your service, which justifies more investment to try to time the transfer. The German-speaking planning tradition is the most concerned with transfer timing, and here, it is done commonly at 10 minutes, occasionally at 5 minutes, and never that I know of at higher frequency.

Easy mode: one central station

If all your buses and trains serve one transit center, then a pulse means that they all run at the same frequency, and all meet at the center at the same time. This doesn’t usually happen on urban rail networks – a multi-line urban rail system exists in a high-ridership, high-frequency context, in which the value of serving a mesh of city center lines is high, and the cost of bringing every subway tunnel to one location is high. Instead, this happens on buses and on legacy regional rail networks.

The pulse can be done at any frequency, but probably the most common is hourly. This is routine in small American towns with last-resort bus networks serving people too poor or disabled to drive. Two and a half years ago a few of us on Transit Twitter did a redesign-by-Twitter of the Sioux City bus network, which has ten bus routes running hourly, all pulsing in city center with timed connections. A similar network often underlies the night buses of a larger city that, in the daytime, has a more complete public transport network, such as Vancouver.

Even here, planners should keep two delicate points in mind. First, on buses in mixed traffic, there is an upper limit to the frequency that can be timetabled reliably. The limit depends on details of the street network – Jarrett Walker is skeptical that timetabling buses that run every 15 minutes is feasible in a typical American city, but Vancouver, with no freeways within a city and a rich arterial grid, manages to do so every 12 minutes on 4th Avenue. A half-hourly pulse is definitely possible, and even Jarrett writes those into his bus redesigns sometimes; a 20-minute pulse is probably feasible as well even in a typical American city. The current practice of hourly service is not good, and, as I point out in the Sioux City post, involves slow, meandering bus routes.

The second point is that once the takt is chosen, say half an hour, the length of each roundtrip had better be an integer multiple of the takt, including a minimal turnaround time. If a train needs 5 minutes to turn, and runs half-hourly, then good times for a one-way trip from city center are 10, 25, 40, 55 minutes; if there is no turnaround at city center, for example if there is through-running, then half as many turnarounds are needed. This means that short- and long-term planning should emphasize creating routes with good trip times. On a bus, this means straightening meanders as needed, and either extending the outer end or cutting it short. On a train, this means speedup treatments to run as fast as necessary, or, if the train has a lot of spare time, opening additional infill stops.

The issue of branching

Branches and pulses don’t mix well. The ideal way to run a system with a trunk and branches is to space the branches evenly. The Berlin S-Bahn runs every 3-4 minute on the Stadtbahn trunk and on the North-South Tunnel, mixing services that run every 10 and 20 minutes at roughly even intervals. In such an environment, timed transfers in city center are impossible. This is of course not a problem given Stadtbahn headways, but becomes serious if frequency is sparser. A one-trunk, two-branch regional rail system’s planners may be tempted to run each branch every half hour and interpolate the schedules to create a 15-minute headway on the trunk, but if there’s a half-hourly pulse, then only one branch can participate in it.

This is visible when one compares S-Bahn and RegionalBahn systems. High-frequency S-Bahn systems don’t use timed transfers in city center, because there is no need. I can get from Jannowitzbrücke to Ostkreuz without consulting a schedule, and I would get to the Ring without consulting a schedule either, so there is no need to time the crossing at Ostkreuz. There may be sporadic transfer timing for individual branches, such as between the S9 branch of the Stadtbahn, which diverts southeast without serving Ostkreuz, and the Ring, but S9 runs every 20 minutes, and this is not a pulse, only a single-direction timed connection.

In contrast, RegionalBahn systems, running at longer ranges and lower frequencies, often tend toward timed transfers throughout. The tradeoff is that they don’t overlie to create high-frequency trunks. In some cases, trains on a shared trunk may even platoon, so that all can make the same timed transfer, if high trunk frequency is not desired; this is how intercity trains are run on the Olten-Bern line, with four trains to a platoon every 30 minutes.

Medium mode: dendritic networks

A harder case than the single pulse is the dendritic network. This means that there is a central pulse point, and also secondary pulse points each acting as a local center. All cases I am aware of involve a mainline rail network, which could be S-Bahn rather than RegionalBahn, and then bus connections at suburban stations.

Already, this involves more complex planning. The reason is that the bus pulse at a suburban station must be timed with trains in both directions. Even if planners only care about connections between the suburban buses and trains toward city center, the pulse has to time with inbound trains for passengers riding from the suburban buses to the city and with outbound trains for passengers riding from the city to the buses. This, in turn, means that the trains in both directions must arrive at the station at approximately the same time. A few minutes of leeway are acceptable, since the buses turn at city center so the connection always has a few minutes of slack, but only a few minutes out of what is often a half-hourly takt.

Trains that run on a takt only meet every interval equal to half the takt. Thus, if trains run half-hourly, they can only have suburban pulses every 15 minutes of travel. This requires planners to set up suburban pulses at the correct interval, and speed up or sometimes slow down the trains if the time between suburban nodes. Here is an example I’ve worked on for a Boston-Worcester commuter train, with pulses in both Framingham and Worcester.

Hard mode: meshes

The next step beyond the dendritic network is the multi-node network whose graph is not simply connected. In such a network, every node must have a timed transfer, which imposes considerable planning constraints. Optimizing such a network is an active topic of research in operations and transportation in European academia.

Positive examples for such networks come from Switzerland. Large capital investments are unavoidable, because there’s always going to be some line that’s slower than it needs to be. The key here is that, as with dendritic networks, nodes must be located at consistent intervals, equal to multiples of half the headway, and usually the entire headway. To make multiple timed transfers, trains must usually be sped up. This is why pulse-based integrated timed transfer networks require considerable planning resources: planning for rolling stock, infrastructure, and the timetable must be integrated (“the magic triangle”) to provide maximum convenience for passengers connecting from anywhere to anywhere.

Density and Rail Transport (Hoisted from Social Media)

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

What is density?

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

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

Density and regional rail

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

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

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

Integrated regional networks

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

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

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

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

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

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

What about low-density places?

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

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

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

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

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

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

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.

No Cafe Cars, Please

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

How much space do cafe cars take?

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

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

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

How valuable are cafes to passengers?

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

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

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

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

Station food

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

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

The Need to Remove Bad Management

I’ve talked a lot recently about bad management as a root cause of poor infrastructure, especially on Twitter. The idea, channeled through Richard Mlynarik, is that the main barrier to good US infrastructure construction, or at least one of the main barriers, is personal incompetence on behalf of decisionmakers. Those decisionmakers can be elected officials, with levels of authority ranging from governors down to individual city council members; political appointees of said officials; quasi-elected power brokers who sit on boards and are seen as representative of some local interest group; public-sector planners; or consultants, usually ones who are viewed as an extension of the public sector and may be run by retired civil servants who get a private-sector salary and a public-sector pension. In this post I’d like to zoom in on the managers more than on the politicians, not because the politicians are not culpable, but because in some cases the managers are too. Moreover, I believe removal of managers with a track record of failure is a must for progress.

The issue of solipsism

Spending any time around people who manage poorly-run agencies is frustrating. I interview people who are involved in successful infrastructure projects, and then I interview ones who are involved in failed ones, and then people in the latter group are divided into two parts. Some speak of the failure interestingly; this can involve a blame game, typically against senior management or politics, but doesn’t have to, for example when Eric and I spoke to cost estimators about unit costs and labor-capital ratios. But some do not – and at least in my experience, the worst cases involve people who don’t acknowledge that something is wrong at all.

I connect this with solipsism, because this failure to acknowledge is paired with severe incuriosity about the rest of the world. A Boston-area official who I otherwise respect told me that it is not possible to electrify the commuter rail system cheaply, because it is 120 years old and requires other investments, as if the German, Austrian, etc. lines that we use as comparison cases aren’t equally old. The same person then said that it is not possible to do maintenance in 4-hour overnight windows, again something that happens all the time in Europe, and therefore there must be periodic weekend service changes.

A year and a half ago I covered a meeting that was videotaped, in which New Haven-area activists pressed $200,000/year managers at Metro-North and Connecticut Department of Transportation about their commuter rail investments. Those managers spoke with perfect confidence about things they had no clue about, saying it’s not possible that European railroads buy multiple-units for $2.5 million per car, which they do; one asserted the US was unique in having wheelchair accessibility laws (!), and had no idea that FRA reform as of a year before the meeting permitted lightly-modified European trains to run on US track.

The worst phrase I keep hearing: apples to apples. The idea is that projects can’t really be compared, because such comparisons are apples to oranges, not apples to apples; if some American project is more expensive, it must be that the comparison is improper and the European or Asian project undercounted something. The idea that, to the contrary, sometimes it’s the American project that is easier, seems beyond nearly everyone who I’ve talked to. For example, most recent and under-construction American subways are under wide, straight streets with plenty of space for the construction of cut-and-cover station boxes, and therefore they should be cheaper than subways built in the constrained center of Barcelona or Stockholm or Milan, not more expensive.

What people are used to

In Massachusetts, to the extent there is any curiosity about rest-of-world practice, it comes because TransitMatters keeps pushing the issue. Even then, there is reticence to electrify, which is why the state budget for regional rail upgrades in the next few years only includes money for completing the electrification of sidings and platform tracks on the already-electrified Providence Line and for short segments including the Fairmount Line, Stoughton Branch, and inner part of the Newburyport and Rockport Lines. In contrast, high platforms, which are an ongoing project in Boston, are easier to accept, and thus the budget includes more widespread money for it, even if it falls short of full high-level platforms at every station in the system.

In contrast, where high platform projects are not so common, railroaders find excuses to avoid them. New Jersey Transit seems uninterested in replacing all the low platforms on its system with high platforms, even though the budget for such an operation is a fraction of that of the Gateway tunnel, which the state committed $2.5 billion to in addition to New York money and requested federal funding. The railroad even went as far as buying new EMUs that are compatible not with the newest FRA regulations, which are similar to UIC ones used in Europe, but with the old ones; like Metro-North’s management, it’s likely NJ Transit’s had no idea that the regulations even changed.

The issue of what people are used to is critical. When you give someone authority over other people and pay them $200,000 a year, you’re signaling to them, “never change.” Such a position can reward ambition, but not the ambition of the curious grinder, but that of the manager who makes other people do their work. People in such a position who do not know what “electronics before concrete” means now never will learn, not will they even value the insights of people who have learned. The org chart is clear: the zoomer who’s read papers about Swiss railroad planning works for the boomer who hasn’t, and if the boomer is uncomfortable with change, the zoomer can either suck it up or learn to code and quit for the private sector.

You can remove obstructionist managers

From time to time, a powerful person who refuses to use their power except in the pettiest ways accidentally does something good. Usually this doesn’t repeat itself, despite the concrete evidence that it is possible to do things thought too politically difficult. For example, LIRR head Helena Williams channeled Long Island NIMBYism and opposed Metro-North’s Penn Station Access on agency turf grounds – it would intrude on what Long Islanders think is their space in the tunnels to Penn Station. But PSA was a priority for Governor Andrew Cuomo, so Cuomo fired Williams, and LIRR opposition vanished.

This same principle can be done at scale. Managers who refuse to learn from successful examples, which in capital construction regardless of mode and in operations of mainline rail are never American and rarely in English-speaking countries, can and should be replaced. Traditional railroaders who say things are impossible that happen all the time in countries they look down on can be fired; people from those same countries will move to New York for a New York salary.

This gets more important the more complex a project gets. It is possible, for example, to build high-speed rail between Boston and Washington for a cost in the teens of billions and not tens, let alone hundreds, but not a single person involved in any of the present effort can do that, because it’s a project with many moving parts and if you trust a railroad manager who says “you can’t have timed overtakes,” you’ll end up overbuilding unnecessary tunnels. In this case, managers with a track record of looking for excuses why things are impossible instead of learning from places that do those things are toxic to the project, and even kicking them up is toxic, because their subordinates will learn to act like that too. The squeaky wheel has to be removed and thrown into the garbage dumpster.

And thankfully, squeaky wheels that get thrown into the dumpster stop squeaking. All of this is possible, it just requires elected officials who have the ambition to take risks to effect tangible change rather than play petty office politics every day. Cuomo is the latter kind of politician, but he proved to everyone that a more competent leader could replace solipsists with curious learners and excusemongers with experts.

I Gave a Talk at Transit Con

An online conference just concluded in which I gave a half-hour presentation about construction costs. Instead of giving my usual spiel, showing parts of our growing database and pointing out patterns, I spent a lot of time on why this is important. I’d written about this before, twice, but I’ve since looked more carefully at an example of two countries that are similar enough in their rail and public transit tradition that their large difference in costs must be the primary reason one has a bigger and more successful urban rail system than the other. I focused on developed countries, that is countries that manifestly have high incomes, good public health, good education, and so on; however, I believe the importance of costs is also a big reason behind delays in public transportation in high-cost developing countries like India.

You can read the slides here; this was recorded, and I’ll update this post with a link when it gets published.

Fare Control and Construction Costs

Proof-of-payment with ungated train stations is a useful technique for reducing construction costs. It simplifies the construction of stations, since there is no need for a headhouse or mezzanine – people can go directly from the street to the platform. A station without fare control requires just a single elevator, or two if side platforms are desired, and can be built shallowly using cut-and-cover. Cities across the size spectrum, perhaps only stopping short of hypercities, should take heed and use this to build urban rail more cheaply.

Is this a common cost control technique?

No. The vast majority of low-construction cost countries use faregates, which is why I was reticent to recommend proof-of-payment as a cost mitigation strategy. Spain, Italy, Korea, and Sweden are all faregated; among the world’s lowest-cost countries, I believe only Finland and Switzerland use proof-of-payment fare collection on urban rail.

However, there are exceptions. In Italy, the Brescia Metro uses proof-of-payment. This is not typical for the country or the region – Italian metros have fare control, like the vast majority of systems outside Germany and Germany-influenced countries. However, because Brescia is small, the system was forced to engage in value engineering, removing scope that would be routine in larger cities like Milan. The majority was built cut-and-cover or above-ground; the typical urban Italian metro is entirely bored. Italian metro systems prefer short stations on new lines to minimize costs and provide capacity through automated operations and extremely high frequency; Brescia takes this to an extreme and has 30-meter trains. Among these cost minimization tactics is the lack of fare control. The result of this entire package is that Brescia spent 915 million euros on a 13.7 km metro system.

Station size and station cost

So far, we believe that the cost of the station, excavation excluded, should be proportional to the floor area. This is based on something told to us in an interview about electrical system costs for the Boston Green Line Extension, which is light rail in a trench rather than a tunneled metro system, so I recommend caution before people repeat this uncritically.

Moreover, on somewhat more evidence, it appears that the cost of station excavation should be proportional to the volume excavated. Some of the evidence for this is circumstantial: media reports and government reports on the construction of such urban rail projects as Second Avenue Subway, Grand Paris Express, and the RER specify the volume of excavation as a measure of the difficulty of construction. But it’s not just circumstantial. In Paris, the depth of some of the GPX stations has led to some construction complications. Moreover, preliminary interviews in Paris suggest, albeit not definitively, that station construction costs are predominantly a matter of dig volume. Finally, the insistence on short platforms and high frequency as a cost saving technique on new-build metro systems in Italy as well as in Denmark and on the Canada Line in Vancouver is suggestive too, even if it says nothing about whether the relationship between volume and cost is linear, degressive, or superlinear.

How does one minimize station costs with POP?

Proof-of-payment means that there is no fare control between the street and the station. This means any of the following ways of constructing station access become available:

  • Cut-and-cover with the platform on level -1, with direct stair and elevator access from the street. The Berlin U-Bahn is built this way, with access points in street medians where available, such as U8 on Brunnenstrasse. It’s easy to build staircases at each end of the platform to increase access, with an elevator in the middle.
  • Bored tunnel with large enough bores to fit the platform within the bore. The Barcelona method for this is to use 12-meter bores, but smaller, cheaper versions exist with smaller trains, for example in Milan. It’s also possible to use double-O-tube TBMs for this, but ordinarily they are more expensive than twin bores. Access involves vertical bores down to the platform with elevators or slant bores with escalators; there is no need for intermediate levels or entry halls.
  • Bored tunnel with cut-and-cover stations, with no mezzanine levels. Here, the dig volume is unchanged, and the saving from lack of fare control is only in the finishes and elevator costs, not the excavation.

It is noteworthy that the most common technique for metro construction, by far, is the last one, where the savings from POP are the smallest. The vast majority of world metros have fare control, including in low-cost countries, and this perhaps makes metro builders not notice how two separate ways of reducing costs – cut-and-cover and POP – interact especially well together. Nonetheless, this is a real saving.

What does this mean?

A technique can be uncommon in low-cost countries and yet be useful in reducing construction costs. It is useful to think of the way Madrid, Milan, Turin, Stockholm, Oslo, Helsinki, and Seoul build their urban rail systems as good, but not always perfect. A trick that these cities might not pay attention to may still be good. The caveat is that it requires a good explanation for why they have not employed it; in the case of Italy, I believe it’s simply that the non-German world views fare control as the appropriate way to run a metro system and POP as a light rail technique and therefore only good for low-volume operations. There may also be backward compatibility issues – Brescia is a new build, like POP Copenhagen, whereas Milan is building extensions on top of a gated system.

Nonetheless, the evidence from station costs, the success of POP operations in Germany even on very busy lines, and the experience of Brescia all suggest that POP is good for metro construction in general. Cities smaller than New York building new systems should use it exclusively, and cities that already have faregates should tear them down to improve passenger circulation and facilitate the construction of POP lines in the future at lower cost.

KWCIMBY

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.