Category: Urban Transit
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.
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.
High Costs are not About Scarcity
I sometimes see a claim in comments here or on social media that the reason American costs are so high is that scarcity makes it hard to be efficient. This can be a statement about government practice: the US government supposedly doesn’t support transit enough. Sometimes it’s about priorities, as in the common refrain that the federal government should subsidize operations and not just capital construction. Sometimes it’s about ideology – the idea that there’s a right-wing attempt to defund transit so there’s siege mentality. I treat these three distinct claims as part of the same, because all of them really say the same thing: give American transit agencies more money without strings attached, and they’ll get better. All of these claims are incorrect, and in fact high costs cannot be solved by giving more money – more money to agencies that waste money now will be wasted in the future.
The easiest way to see that theories of political precarity or underresourcing are wrong is to try to see how agencies would react if they were beset mostly by scarcity as their defenders suggest. For example, the federal government subsidizes capital expansion and not operations, and political transit advocates in the United States have long called for operating funds. So, if transit agencies invested rationally based on this restrictions, what would they do? We can look at this, and see that this differs greatly from how they actually invest.
The political theory of right-wing underresourcing is similarly amenable to evaluation using the same method. Big cities are mostly reliant not on federal money but state and local money, so it’s useful to see how different cities react to different threat levels of budget cuts. It’s also useful to look historically at what happened in response to cuts, for example in the Reagan era, and spending increases, for example in the stimulus in the early Obama era and again now.
How to respond to scarcity
A public transit agency without regular funding would use the prospects of big projects to get other people’s money (OPM) to build longstanding priorities. This is not hypothetical: the OPM effect is real, and for example people have told Eric and me that Somerville used the original Green Line Extension to push for local amenities, including signature stations and a bike lane called the Community Path. In New York, the MTA has used projects that are sold to the public as accessibility benefits to remodel stations, putting what it cares about (cleaning up stations) on the budget of something it does not (accessibility).
The question is not whether this effect is real, but rather, whether agencies are behaving rationally, using OPM to build useful things that can be justified as related to the project that is being funded. And the answer to this question is negative.
For every big federally-funded project, one can look at plausible tie-ins that can be bundled into it that enhance service, which the Somerville Community Path would not. At least the ongoing examples we’ve been looking at are not so bundled. Consider the following misses:
Green Line Extension
GLX could include improvements to the Green Line, and to some extent does – it bundles a new railyard. However, there are plenty of operational benefits on the Green Line that are somewhere on the MBTA’s wishlist that are not part of the project. Most important is level boarding: all vehicles have a step up from the platform, because the doors open outward and would strike the platform if there were wheelchair-accessible boarding. The new vehicles are different and permit level boarding, but GLX is not bundling full level boarding at all preexisting stations.
East Side Access and Gateway
East Side Access and Gateway are two enormous commuter rail projects, and are the world’s two most expensive tunnels per kilometer. They are tellingly not bundled with any capital improvements that would boost reliability and throughput: completion of electrification on the LIRR and NJ Transit, high platforms on NJ Transit, grade separations of key junctions between suburban branches.
The issue of operating expenses
More broadly, American transit agencies do not try to optimize their rail capital spending around the fact that federal funding will subsidize capital expansion but not operations. Electrification is a good deal even for an agency that has to fund everything from one source, cutting lifecycle costs of rolling stock acquisition and maintenance in half; for an agency that gets its rolling stock and wire from OPM but has to fund maintenance by itself, it’s an amazing investment with no downside. And yet, American commuter rail agencies do not prioritize it. Nor do they prioritize high platforms – they invest in them but in bits and pieces. This is especially egregious at SEPTA, which is allowed by labor agreement to remove the conductors from its trains, but to do so needs to upgrade all platforms to level boarding, as the rolling stock has manually-operated trap doors at low-platform stations.
Agencies operating urban rail do not really invest based on operating cost minimization either. An agency that could get capital funding from OPM but not operating funding could transition to driverless trains; American agencies do not do so, even in states with weak unions and anti-union governments, like Georgia and Florida. New York specifically is beset by unusually high operating expenses, due to very high maintenance levels, two-person crews, and inefficient crew scheduling. If the MTA has ever tried to ask for capital funding to make crew scheduling more efficient, I have not seen it; the biggest change is operational, namely running more off-peak service to reduce shift splitting, but it’s conceivable that some railyards may need to be expanded to position crews better.
Finally, buses. American transit agencies mostly run buses – the vast majority of US public transport service is buses, even if ridership splits fairly evenly between buses and trains. The impact of federal aid for capital but not operations is noticeable in agency decisions to upgrade a bus route to rail perhaps prematurely in some medium-size cities. It’s also visible in bus replacement schedules: buses are replaced every 12 years because that’s what the Federal Transit Administration will fund, whereas in Canada, which has the same bus market and regulations but usually no federal funding for either capital or operations, buses are made to last slightly longer, around 15 years.
It’s hard to tell if American transit agencies are being perfectly rational with bus investment, because a large majority of bus operating expenses are the driver’s wage, which is generally near market rate. That said, the next largest category is maintenance, and there, it is possible to be efficient. Some agencies do it right, like the Chicago Transit Authority, which replaces 1/12 of its fleet every year to have long-term maintenance stability, with exactly 1/12 of the fleet up for mid-life refurbishment each year. Others do it wrong – the MTA buys buses in bunches, leading to higher operating expenses, even though it has a rolling capital plan and can self-fund this system in years when federal funds are not forthcoming.
Right-wing budget cuts
Roughly the entirety of the center-right policy sphere in the United States is hostile to public transportation. The most moderate and least partisan elements of it identify as libertarian, like Cato and Reason, but mainstream American libertarianism is funded by the Koch Brothers and tends toward climate change denial and opposition to public transportation even where its natural constituency of non-left-wing urbane voters is fairly liberal on this issue. The Manhattan Institute is the biggest exception that I’m aware of – it thinks the MTA needs to cut pension payments and weaken the unions but isn’t hostile to the existence of public transportation. In that environment, there is a siege mentality among transit agencies, which associate any criticism on efficiency grounds as part of a right-wing strategy to discredit the idea of government.
Or is there?
California does not have a Republican Party to speak of. The Democrats have legislative 2/3 majorities, and Senate elections, using a two-round system, have two Democrats facing each other in the runoff rather than a Democrat and a Republican. In San Francisco, conservatism is so fringe that the few conservatives who remain back the moderate faction of city politics, whose most notable members are gay rights activist and magnet for alt-right criticism Scott Wiener, (until his death) public housing tenant organizer Ed Lee, and (currently) Mayor London Breed, who is building homeless shelters in San Francisco over NIMBY objections. The biggest organized voices in the Bay Area criticizing the government on efficiency grounds and asserting that the private sector is better come from the tech industry, and usually the people from that industry who get involved with politics are pro-immigration climate change hawks. Nobody is besieging the government in the Bay Area. Nor is anybody besieging public transit in particular – it is popular enough to routinely win the required 2/3 majority for tax hikes in referendums.
In New York, this is almost as true. The Democrats have a legislative 2/3 majority as of the election that just concluded, there does not appear to be a serious Republican candidate for either mayor or governor right now, and the Manhattan Institute recognizes its position and, on local issues of governance, essentially plays the loyal opposition. The last Republican governor, George Pataki, backed East Side Access, trading it for Second Avenue Subway Phase 1, which State Assembly Speaker Sheldon Silver favored.
One might expect that the broad political consensus that more public transportation is good in New York and the Bay Area would enable long-term investment. But it hasn’t. The MTA has had five-year capital plans for decades, and has known it was going to expand with Second Avenue Subway since the 1990s. BART has regularly gotten money for expansion, and Caltrain has rebuilt nearly all of its platforms in the last generation without any attempt at level boarding.
How a competent agency responds to scarcity
American transit agencies’ extravagant capital spending is not in any way a rational response to any kind of precarity, economic or political. So what is? The answer is, the sum total of investment decisions made in most low-cost countries fits the bill well.
Swiss planning maxims come out of a political environment without a left-wing majority; plans for high-speed rail in the 1980s ran into opposition on cost grounds, and the Zurich U-Bahn plans had lost two separate referendums. The kind of planning Switzerland has engaged in in the last 30 years to become Europe’s strongest rail network came precisely because it had to be efficient to retain public trust to get funds. The Canton of Zurich has to that end had to come up with a formula to divide subsidies between different municipalities with different ideas of how much public services they want, and S-Bahn investment has always been about providing the best passenger experience at the lowest cost.
Elsewhere in Europe, one sees the same emphasis on efficiency in the Nordic countries. Scandinavia as a whole has a reputation for left-wing politics, because of its midcentury social democratic dominance and strong welfare states. But as a region it also practices hardline monetary austerity, to the point that even left-led governments in Sweden and Finland wanted to slow down EU stimulus plans during the early stages of the corona crisis. There is a great deal of public trust in the state there, but it is downstream of efficiency and not upstream of it – high-cost lines get savaged in the press, which engages in pan-Nordic comparisons to assure that people get value for money.
Nor is there unanimous consensus in favor of public transportation anywhere in Europe that I know of, save Paris and London. Center-right parties support cars and oppose rail in Germany and around it. Much of the Swedish right loathes Greta Thunberg, and the center-right diverted all proceeds from Stockholm’s congestion charge to highway construction. The British right has used the expression “war on the motorist” even more than the American right has the expression “war on cars.” The Swiss People’s Party is in government as part of the grand coalition, has been the largest party for more than 20 years, and consistently opposes rail and supports roads, which is why the Lötschberg Base Tunnel’s second track is only 1/3 complete.
Most European transit agencies have responded effectively to political precarity and budget crunches. They invest to minimize future operating expenses, and make long-term plans as far as political winds permit them to. American transit agencies don’t do any of this. They’re allergic to mainline rail electrification, sluggish about high platforms, indifferent to labor-saving signaling projects, hostile to accessibility upgrades unless sued, and uncreative about long-term operating expenses. They’re not precarious – they’re just incompetent.
Friends Don’t Let Friends Build PPPs
Three examples of public-private partnerships screwing up urban transit are on my mind. The Canada Line in Vancouver is not new to me – I was poking around a few years ago. But the other two in this post are. The Maryland Purple Line in the suburbs of Washington was supposed to be the smooth PPP offering low-risk orbital light rail connecting suburbs to other suburbs without having to go through Downtown Washington, and now it is in shambles because the contractor walked away. Milan is not a new example either, but it is new to me, as we’ve discovered it during the construction costs project comparing high American (and British) costs to low Southern European ones; even there, the PPP bug bit, leading not so much to high capital costs but to high future operating charges. In no case is such a PPP program good government; the bulk of construction and risk must always lie in the public sector, and if your public sector is too incompetent to build things itself, as in the United States, then it’s equally incompetent at overseeing a PPP, as we’re seeing in Maryland. Don’t do this.
Washington: the Purple Line
Maryland planned on building two major urban rail projects last decade, stretching into the current one: the Red Line and the Purple Line. The Red Line was to be a conventional public project to build a subway in Baltimore, mostly serving low-income West Baltimore neighborhoods. The Purple Line, a light rail project in the DC suburbs acting as an orbital for Metro, was designed as a PPP. Governor Larry Hogan canceled the Red Line, most likely for racist reasons. The physical construction costs per rider were higher on the Red Line, but the overall disbursement including very high operating charges made the Purple Line more expensive, and yet Hogan kept the more expensive system and tossed the cheaper one.
One might expect that the PPP structure of the Maryland Purple Line would allow it to at least resist cost escalation – the risk was put entirely on the private contractor. And yet, the opposite happened. Costs turned out to be higher than expected, so the contractor just quit. Once the contract is signed, no matter what it says, the risk is in practice public, and this is no exception. The contractor stopped all work and left the region with a linear swath of ripped up roads; eventually the concessionaire and the state came into a settlement in which the state would pay $250 million extra and the concessionaire would hire a new contractor. The cost overrun was $800 million and the state said that the deal was going to save taxpayers $500 million, but what it signals is that even with very high public-sector payouts over decades that intend to put the entirety of the risk on the private concession, the public sector shares a high proportion of the risk, and the private bidders know this. This is a lose-lose situation and under no circumstances should countries put themselves in it.
Vancouver
Vancouver provides another good example of PPPs and operating costs. SkyTrain operates driverless equipment throughout the system, which means that operating costs should be low, and, moreover, should not depend on train size much. The Expo and Millennium Lines, built and operated publicly, cost C$3.20 to run per car-km, cheaper than on any system for which I have data (mostly very large ones plus Oslo) and less than half as expensive as the major European systems. But the Canada Line, operated by a concessionaire as part of a PPP scheme, costs $17.90/car-km, which is considerably worse than any system for which I have data except PATH. Even taking into account that the Canada Line cars are somewhat bigger, this is a difference of a factor of more than 3.
This is not a matter of economies of scale. The Canada Line’s trunk runs every 3.5 minutes most of the day, which is better than the vast majority of non-driverless systems I am familiar with off-peak, so the high costs there cannot be ascribed to poor utilization. In fact, before the Evergreen extension of the Millennium Line opened in 2016, the two systems’ total operating costs were almost identical but the operating costs per car-km were about 3.5 times worse on the Canada Line – economies of scale predict that unit costs should be degressive, not almost flat.
Milan
Marco Chitti is busy collecting information and conducting interviews regarding subway construction in Italy as part of our construction costs report. Italian costs are low, which makes it feasible to build metros even in very small cities like Brescia, where per Wikipedia the cost of the metro was around €65 million per km and €15,000 per weekday rider. However, the use of PPPs has not been good in the places where it happened, due to fiscal austerity following the Great Recession.
- What is the impact on the cost of the PPP? The impact on costs of the potential transfer of risk from the Public to the Private is hard to calculate, but it appears to have an impact more on higher gross operational costs (the fee that the Municipality will pay in the 26 years of the concession for the operation and pay back a return to the private operators) than on the actual construction cost. But that is unclear yet. A bit of detail: the municipality will pay to the concessionaire a 1.09 €/passenger as a minimum granted fee up to 84 million passengers/year, 0.45€/passenger for each additional user up to a maximum determined as an increase of the IRR of 2 percentage points more than the “base IRR” of 5.93%. That means that this is basically the rate at which the private investors are de facto borrowing the money to the municipality, with most of the risk from low ridership transferred to the municipality. What makes calculations complicate is that the city is directly a majority stakeholder of the concessionaire Metro M4 S.p.A. and also, indirectly, as the owner of ATM, which will be the “private” operator. It’s very blurred compared to other PPP schemes where the concessionaire is 100% private (like M5).
- PPP emerges as a stratagem to finance the project without increasing the municipal public debt. The PPP schemes is used to compensate for the lack of local public funds matching the national ones, limited due to the debt cap imposed by the so-called “internal Stability Compact”, an austerity measure implemented after the 2011 debt crisis, which strongly limits the capacity of local governments to borrow money for infrastructure projects. It was suspended in 2016.
Note that contra the plan to build the system without public debt, the PPP does in fact include borrowing. It’s opaque, but the payment per rider is a form of borrowing. Driverless metro operating costs are lower than €1.09 per unlinked trip. The Expo and Millennium Lines cost C$1.55, which in PPP terms is about €0.90, and feature much longer trips, as the Expo Line is 36 km long and one-tailed, which means many people ride end-to-end, whereas Milan M4 is to be 15 km and two-tailed, which means few trips are longer than half the total. In effect, this is high-interest borrowing, kept off the books in an atmosphere of strict budgetary austerity
Don’t do this
PPP-built lines do not have to have high construction costs. The Canada Line was cheap to build – it was Canada’s last reasonable-cost subway, and since then costs have exploded around the country. M4 in Milan is inexpensive as well, around €110 million per kilometer at current estimates even while going underneath older subways in city center. The current annual ridership projection of M4, 87 million, means that the current projected cost per weekday trip is €6,000, which represents an enormous social surplus in a region that builds up to around €30,000-40,000 before even pro-transit activists demand cancellation.
But in those cases, the structure of the contract keeps the operating costs artificially high, privatizing what should be public-sector profit from building a very inexpensive-to-operate system. This is especially bad if it is bundled into construction costs as an up-front payment, as in Maryland. In Maryland, the extra operating costs raised the construction cost well above the maximum level that is acceptable to the public transportation community over here, and in the United States too, such lines tend to be under threat of cancellation from fiscally conservative governors if they are not portrayed as pro-market PPPs. But those PPPs then have higher costs and, through poor risk allocation, lead to the worst of both worlds: the private concessionaire increases costs in order to deal with the risk of escalation, but if the risk exceeds prior estimates, then the state remains on the hook.
Don’t do this. One can to some extent understand why Italy was forced into this position at the bottom of the financial crisis. This isn’t such a situation – all countries in Europe are engaging in large discretionary deficit spending nowadays, as the market appears to believe that not only will corona pass, but also the new vaccines developed will help prevent the common cold and the flu in the near future, increasing future health outcomes and improving productivity through less lost sick time. In the United States, a $2 trillion stimulus is sold as just the first of two steps, because there’s fiscal room. You, even as a state or local government, can find money in the budget for more spending – raise taxes or sell bonds, and do so transparently. Don’t take opaque high-interest loans just to tell the public that you haven’t borrowed on the open market. It’s not worth it.
Costs Matter: Some Examples
A bunch of Americans who should know better tell me that nobody really cares about construction costs – what matters is getting projects built. This post is dedicated to them; if you already believe that efficiency and social return on investment matter then you may find these examples interesting but you probably are not looking for the main argument.
Exhibit 1: North America
Vancouver
I wrote a post focusing on some North American West Coast examples 5 years ago, but costs have since run over and this matters from the point of view of building more in the future. In the 2000s and 10s, Vancouver had the lowest construction costs in North America. The cost estimate for the Broadway subway in the 2010s was C$250 million per kilometer, which is below world median; subsequently, after I wrote the original post, an overrun by a factor of about two was announced, in line with real increases in costs throughout Canada in the same period.
Metro Vancouver has always had to contend with small, finite amounts of money, especially with obligatory political waste. The Broadway subway serves the two largest non-CBD job centers in the region, the City Hall/Central Broadway area and the UBC, but in regional politics it is viewed as a Vancouver project that must be balanced with a suburban project, namely the lower-performing Surrey light rail. Thus, the amount of money that was ever made available was about in line with the original budget, which is currently only enough to build half the line. Owing to the geography of the West Side, half a line is a lot less than half as good as the full line, so Vancouver’s inability to control costs has led to worse public transportation investment.
Toronto
Like Vancouver, Toronto has gone from having pretty good cost control 20 years ago to having terrible cost control today. Toronto’s situation is in fact worse – its urban rail program today is a contender for the second most expensive per kilometer in the world, next to New York. The question of whether it beats Singapore, Hong Kong, London, Melbourne, Manila, Qatar, and Los Angeles depends on project details, essentially on scoring which of these is geologically and geographically the hardest to build in assuming competent leadership, which is in short supply in all of these cities. I am even tempted to specifically blame the most recent political interference for the rising costs, just as the adoption of design-build in the 2000s as an in-vogue reform must be blamed for the beginning of the cost blowouts.
The result is that Toronto is building less stuff. It’s been planning a U-shaped Downtown Relief Line for decades, since only the Yonge-University-Spadina (“YUS”) line serves downtown proper and is therefore overcrowded. However, it’s not really able to afford the full line, and hence it keeps downgrading it with various iterations, right now to an inverted L for the Ontario Line project.
Los Angeles
Los Angeles’s costs, uniquely in the United States, seemed reasonable 15 years ago, and no longer are. This, as in Canada, can be seen in building less stuff. High-ranking officials at Los Angeles Metro explained to me and Eric that the money for capital expansion is bound by formulas decided by referendum; there is a schedule for how to spend the money as far as 2060, which means that anything that is not in the current plan is not planned to be built in the next 40 years. Shifting priorities is not really possible, not with how Metro has to buy off every regional interest group to ensure the tax increases win referendums by the required 2/3 supermajority. And even then, the taxes imposed are rising to become a noticeable fraction of consumer spending – even if California went to majority vote, its tax capacity would remain very finite.
New York
The history of Second Avenue Subway screams “we would have built more had costs been lower.” People with deeper historic grounding than I do have written at length about the problems of the Independent Subway System (“IND”) built in the 1920s and 30s; in short, construction costs were in today’s terms around $140 million per km, which at the time was a lot (London and Paris were building subways for $30-35 million/km), and this doomed the Second System. But the same impact of high costs, scaled to the modern economy, is seen for the current SAS project.
The history of SAS is that it was planned as a single system from 125th Street to Hanover Square. The politician most responsible for funding it, Sheldon Silver, represented the Lower East Side. But spending capacity was limited, and in particular Silver had to trade that horse for East Side Access serving Long Island, which was Governor George Pataki’s base. The package was such that SAS could only get a few billion dollars, whereas at the time the cost estimate for the entire 13-km line was $17 billion. That’s why SAS was chopped into four phases, starting on the Upper East Side. Silver himself signed off on this in the early 2000s even though his district would only be served in phase four: he and the MTA assumed that there would be further statewide infrastructure packages and the entire line would be complete by 2020.
Exhibit 2: Israel
Israel is discussing extending the Tel Aviv Metro. It sounds weird to speak of extensions when the first line is yet to open, but that line, the Red Line, is under construction and close enough to the end that people are believing it will happen; Israelis’ faith that there would ever be a subway in Tel Aviv was until recently comparable to New Yorkers’ faith until the early 2010s that Second Avenue Subway would ever open. The Red Line is a subway-surface Stadtbahn, as is the under-construction Green Line and the planned Purple Line. But metropolitan Tel Aviv keeps growing and is at this point an economic conurbation of about 3-4 million people, with a contiguous urban core of 1.5 million. It needs more. Hence, people keep discussing additions. The Ministry of Finance, having soured on the Stadtbahn idea, bypassed the Ministry of Transport and introduced a complementary three-line underground driverless metro system.
The cost of the system is estimated at 130-150 billion shekels, which is around $39 billion. This is not a sum Israelis are used to seeing for a government project. It’s about two years’ worth of IDF spending, and Israeli is a militarized society. It’s about 10% of annual GDP, which in American or EU-wide terms would be $2 trillion. The state has many competing budget priorities, and there are so many other valid claims on the state coffers. It is therefore likely that the metro project’s construction will stretch over many years, not out of planning latency but out of real resource limits. People in Israel understand that Gush Dan has severe traffic congestion and needs better transportation – this is not a point of political controversy in a society that has many. But this means the public is willing to spend this amount of money over 15-20 years at the shortest. Were costs to double, in line with the costs in most of th Anglosphere, it would take twice as long; were they to fall in half, in line with Mediterranean Europe, it would take half as long.
Exhibit 3: Spain
As the country with the world’s lowest construction costs for infrastructure, Spain builds a lot of it, everywhere. This includes places where nobody else would think to build a metro tunnel or an airport or a high-speed rail line; Spain has the world’s second longest high-speed rail network, behind China. Many of these lines probably don’t even make sense within a Spanish context – RENFE at best operationally breaks even, and the airports were often white elephants built at the peak of the Spanish bubble before the 2008 financial crisis.
One can see this in urban rail length just as in high-speed rail. Madrid Metro is 293 km long, the third longest in Europe behind London and Moscow. This is the result of aggressive expansion in the 1990s and 2000s; new readers are invited to read Manuel Melis Maynar’s writeup of how when he was Madrid Metro’s CEO he built tunnels so cheaply. Expansion slowed down dramatically after the financial crisis, but is starting up again; the Spanish economy is not good, but when one can build subways for €100 million per kilometer, one can build subways that other cities would not. In addition to regular metros, Madrid also has regional rail tunnels – two of them in operation, going north-south, with a third under construction going east-west and a separate mainline rail tunnel for cross-city high-speed rail.
Exhibit 4: Japan
Japan practices economic austerity. It wants to privatize Tokyo Metro, and to get the best price, it needs to keep debt service low. When the Fukutoshin Line opened in 2008, Tokyo Metro said it would be the system’s last line, to limit depreciation and interest costs. The line amounted to around $280 million/km in today’s money, but Tokyo Metro warned that the next line would have to cost $500 million/km, which was too high. The rule in Japan has recently been that the state will fund a subway if it is profitable enough to pay back construction costs within 30 years.
Now, as a matter of politics, on can and should point out that a 30-year payback, or 3.3% annual interest, is ridiculously high. For one, Japan’s natural interest rate is far lower, and corporations borrow at a fraction of that interest; JR Central is expecting to be paying down Chuo Shinkansen debt until the 2090s, for a project that is slated to open in full in the 2040s. However, if the state changes its rule to something else, say 1% interest, all that will change is the frontier of what it will fund; lines will continue to be built up to a budgetary limit, so that the lower the construction costs, the more stuff can be built.
Conclusion: the frontier of construction
In a functioning state, infrastructure is built as it becomes cost-effective based on economic growth, demographic projections, public need, and advances in technology. There can be political or cultural influences on the decisionmaking process, but they don’t lead to huge swings. What this means is that as time goes by, more infrastructure becomes viable – and infrastructure is generally built shortly after it becomes economically beneficial, so that it looks right on the edge of viability.
This is why megaprojects are so controversial. Taiwan High-Speed Rail and Korea Train Express are both very strong systems nowadays. Total KTX ridership stood at 89 million in 2019 and was rising on the eve of corona, thanks to Korea’s ability to build more and more lines, for example the $69 million/km, 82% underground SRT reverse-branch. THSR, which has financial data on Wikipedia, has 67 million annual riders and is financially profitable, returning about 4% on capital after depreciation, before interest. But when KTX and THSR opened, they both came far below ridership projections, which were made in the 1990s when they had much faster economic convergence before the 1997 crisis. They were viewed as white elephants, and THSR could not pay interest and had to refinance at a lower rate. Taiwan and South Korea could have waited 15 years and only opened HSR now that they have almost fully converged to first-world Western incomes. But why would they? In the 2000s, HSR in both countries was a positive value proposition; why skip on 15 years of good infrastructure just because it was controversially good then and only uncontroversially good now?
In a functioning state, there is always a frontier of technology. The more cost-effective construction is, the further away the frontier is and the more infrastructure can be built. It’s likely that a Japan that can build subways for Korean costs is a Japan that keeps expanding the Tokyo rail network, because Japan is not incompetent, just austerian and somewhat high-cost. The way one gets more stuff built is by ensuring costs look like those of Spain and Korea and not like those of Japan and Israel, let alone those of the United States and Canada.
More on Station Costs
Talking to Marco Chitti about the history of Italian construction always fills me with hope. He’s been gathering data about metro construction in Milan and Rome, and told Elif, Eric, and me about the issue of building through constrained areas. Historic city centers are constrained because tunneling can damage buildings – the first two lines in Milan, built in the 1950s and 60s at abnormally low costs, caused some damage to buildings, since they involved cut-and-cover under streets only 12-15 meters wide. The good news is that tunneling with a tunnel boring machine is fine now. Stations remain an enormous challenge – but the conversation did fill me with optimism about future construction in cities that were not global imperial capitals 2,000 years ago.
TBM technology
Tunnel-boring machines have advanced to the point of being archeology-safe. Italian heritage protection laws from the 2000s forbid any risk to historic buildings and historic sites, but TBM technology at this point allows preserving artifacts. It involves injecting a gel ahead of the cutting edge, which is not supposed to be a cost-raiser.
The result is that tunneling is cheap. This is not a matter of low wages – in fact, Marco cites higher wages for Italian skilled workers who staff TBMs, up to €4,500 a month net, which rises to about €9,000 gross with social contributions. These are based on a nationwide scale that only weakly varies with location, which helps explain why Naples costs are not low despite the region’s low incomes.
Station construction
Station construction costs vary immensely by location. In Rome, on the same project, stations in a suburban part of the city might be €60-70 million. This does not mean construction is trivially easy: Rome’s suburbs still often host historic sites, having been home to patrician villas in Antiquity, and in fact the word suburb dates to that era. However, it’s relatively safe, and I don’t think Line C ran into such sites.
Then in the most constrained parts of the city, things are different. The extension plans for Line C deeper into city center have station costs in the €400-600 million range. This is not what things cost everything within Rome, or even everywhere within the densely-built parts of the city. But the Line C extension passes through the most historic sites. An already-under construction segment will go to the Colosseum, and a planned extension deeper into city center is to go to Piazza Venezia, at the Wedding Cake, and it is that station that is projected to cost €600 million.
The reason for the high cost is that it is not possible to do archeology- and building-safe cut-and-cover. Piazza Venezia doesn’t quite have enough room for a cut-and-cover dig of a full-length station. It is fed by a wide street, the Via Fori Imperali, and I asked Marco why not build cut-and-cover there, but he pointed out that the street goes through the historic Forum. It is in fact elevated over the ruins; any cut-and-cover there would endanger the Forum, and is not acceptable.
Without cut-and-cover, the only alternative is to mine the stations. Rome investigated the option of large-diameter TBMs on the Barcelona L9 model and found it infeasible, since the tunnels are so big they might themselves cause some building damage. Once the stations are mined from a small shaft, their costs explode. Second Avenue Subway built stations using the same method, and had similar per-station construction costs.
The good news
Mined station construction is in practically all cases not necessary. New Yorkers talk about the city’s high built-up density as a reason why costs are high. But in terms of actual stuff in the way of a tunnel, there’s less in New York than in Rome or Istanbul, which has even lower construction costs.
In fact, there is a line in Rome that is rather similar in urban geography to Second Avenue Subway: the Line B1 branch. It runs under a 27 meter wide street flanked by modern buildings that are about 9 stories tall above ground but also have underground parking, Italy having such a car culture that the middle class expects to own cars even in Rome. The cost: €527 million for 3.9 km, in 2010-15.
Moreover, the hard rock in New York should make it easier to build stations while maintaining building safety. Manhattan’s schist is brittle and therefore requires concrete lining, unlike the more uniform gneiss of Stockholm, famously forming natural arches that are pretty to look at from within the tunnels. However, it is still better soil for construction than the sand of Berlin’s U5 extension, to be opened next month, or the alluvial soil of Amsterdam.
The explanation Marco gives concerning station construction is physical and not institutional. This means it should transplant well into another setting – which it does!
In Berlin, the city-center U5 extension, including U55, is in today’s money around €240 million/km. The stations look like cut-and-cover to me, and if they’re not then it comes from severe NIMBYism since the line goes under the very wide Unter den Linden, but one of the stations is basically under the river and another is under U6 and involves moving the U6 station, and the sandy soil is genuinely bad to tunnel through. Suburban extensions in Berlin, with easy cut-and-cover stations, are consistently in the €100-150 million/km range, which is barely higher than the non-Forum Italian range. So Berlin looks fine, and just needs to invest resources into U- and S-Bahn extensions and not into extending the A 100 motorway.
Can New York have what Italy has?
Almost certainly! Second Avenue is not an old or narrow street by Italian standards. Nor are any of the other streets slated for subway construction in New York, such as Nostrand, Utica, and even 125th. Importing construction techniques from Italy and Germany should be feasible. There may be problems with local politics – New Yorkers absolutely hate admitting that another city may be better than theirs in any way, and this makes learning harder. But it is not impossible, and so far there do not seem to be any physical or economic obstacles to doing so.
The German Way of Building Rapid Transit
Continuing my series on different traditions of building urban rapid transit, today it’s time for Germany and Austria, following the posts on the US, the Soviet bloc, Britain, and France. Germany had a small maritime empire by British and French standards and lost it all after World War 1, but has been tremendously influential on its immediate neighbors as a continental power. This is equally true of rapid transit: Germany and Austria’s rail traditions have evolved in a similar direction, influential also in Switzerland, Denmark, the Netherlands, and Belgium to varying extents.
S-Bahns and U-Bahns
Germany is one of the origins of urban regional rail, called S-Bahn here in contrast with the U-Bahn subway. The first frequent urban rail service in the world appeared in London in 1836, but trains ran every 20 minutes and the stop spacing was only borderline urban. Berlin in contrast innovated when it opened the east-west elevated Stadtbahn in 1882, running frequent steam trains with local spacing.
As elevated steam-powered urban rail, the Stadtbahn was not particularly innovative. New York had already been running such service on its own els going back to 1872. But the Stadtbahn differed in being integrated into the mainline rail system from the start. Berlin already had the Ringbahn circling the city’s then-built up area to permit freight trains to go around, but it still built the Stadtbahn with four tracks, two dedicated to local traffic and two to intercity traffic. Moreover, it was built to mainline rail standards, and was upgraded over time as these standards changed with the new national rail regulation of 1925. This more than anything was the origin of the concept of regional rail or S-Bahn today.
Vienna built such a system as well, inspired by many sources, including Berlin, opening in 1898. Hamburg further built a mainline urban rail connection between Hauptbahnhof and Altona, electrifying it in 1907 to become the first electrified S-Bahn in the world. Copenhagen, today not particularly German in its transportation system, built an S-Bahn in the 1930s, naming it S-tog after the German term.
However, German cities that built such S-Bahn systems would also build separate U-Bahn systems. U-Bahns in Germany have short stop spacing and tend to mostly serve inner areas: for example, on this map of Munich, the U-Bahn is in blue, and the trams are in red. Berlin has some farther-reaching U-Bahn lines, especially U7, a Cold War line built when the West got the U-Bahn and the East got the S-Bahn; had the city not been divided, it’s unlikely it would have been built at all.
Some of the early U-Bahns were even elevated, similarly to New York subway lines and a few Paris Métro lines. Hamburg’s operator is even called Hochbahn in recognition of the elevated characteristic of much of its system. Like Paris and unlike New York, those elevated segments are on concrete viaducts and not steel structures, and therefore the trains above are not very noisy, generally quieter than the cars at street level.
Light rail and Stadtbahns
The early els of Berlin and Vienna were called Stadtbahn when built in the 19th century, but since the 1960s, the term has been used to refer to mixed subway-surface systems.
Germany had long been a world leader in streetcar systems – the first electric streetcar in the world opened in Berlin in 1881. But after World War Two, streetcars began to be viewed as old-fashioned and just getting in the way of cars. West German cities generally tore out their streetcars in their centers, but unlike American or French cities, they replaced those streetcars with Stadtbahn tunnels and retained the historic streetcar alignments in outer neighborhoods feeding those tunnels.
The closure of the streetcars was not universal. Munich and Vienna retained the majority of their tram route-length, though they did close lines parallel to the fully grade-separated U-Bahn systems both cities built postwar. Many smaller cities retained their trams, like Augsburg and Salzburg, though this was generally more consistent in the Eastern Bloc, which built very little rapid transit (East Berlin) or severed itself from the German planning tradition and Sovietized (Prague, Budapest).
The Stadtbahn concept is also extensively used in Belgium, where it is called pre-metro; the Vienna U-Bahn and even the generally un-German Stockholm T-bana both have pre-metro history, only later transitioning to full grade separation. Mixed rapid transit-streetcar operations also exist in the Netherlands, but not in the consistent fashion of either the fast-in-the-center-slow-outside Stadtbahn or its fast-outside-slow-in-the-center inverse, the Karlsruhe model of the tram-train.
Network design
Rail network design in German-speaking cities is highly coordinated between modes but is not very systematic or coherent.
The coordination means that different lines work together, even across modes. In the post about France, I noted that the Paris Métro benefited from coordinated planning from the start, so that on the current network, there is only one place where two lines cross without a transfer. This is true, but there are unfortunately many places where a Métro line and an RER line cross without a transfer; the central RER B+D tunnel alone crosses three east-west Métro lines without a transfer. In Berlin, in contrast, there are no missed connections on the U-Bahn and the S-Bahn, and only one between the U-Bahn and S-Bahn, which S21 plans do aim to fix. Hamburg has two missed connections on the U-Bahn and one between the U- and S-Bahn. Munich has no missed connections at all.
But while the lines work well as a graph, they are not very coherent in the sense of having a clear design paradigm. Berlin is the most obvious example of this, having an U-Bahn that is neither radial like London or Moscow nor a grid like Paris. This is not even a Cold War artifact: U6 and U8 are parallel north-south lines, and have been since they opened in the 1920s and early 20s. Hamburg and Vienna are haphazard too. Munich is more coherent – its U-Bahn has three trunk lines meeting in a Soviet triangle – but its branching structure is weird, with two rush hour-only reverse-branches running as U7 and U8. The larger Stadtbahn networks, especially Cologne, are a hodgepodge of mergers and splits.
Fares
The German planning tradition has distinguishing characteristics that are rare in other traditions, particularly when it comes to fare payment – in many other respects, the Berlin U-Bahn looks similar to the Paris Métro, especially if one ignores regional rail.
Proof of payment: stations have no fare barriers, and the fare is enforced entirely with proof of payment inspections. This is common globally on light rail (itself partly a German import in North America) and on European commuter rail networks, but in Germany this system is used even on U-Bahns and on very busy S-Bahn trunks like Munich and Berlin’s; in Paris there’s POP on the RER but only in the suburbs, not in the city.
Unstaffed stations: because there are no fare barriers, stations do not require station agents, which reduces operating expenses. In Berlin, most U-Bahn stations have a consistent layout: an island platform with a stairway exit at each end. This is also common in the rest of the German-speaking world. Because there is no need for fare barriers, it is easy to make the stations barrier-free – only one elevator is needed per station, and thus Berlin is approaching fully wheelchair accessibility at low cost, even though it’s contemporary with New York (only 25% accessible) and Paris (only 3% accessible, the lowest among major world metros).
Fare integration: fares are mode-neutral, so riding an express regional train within the city costs the same as the U-Bahn or the bus, and transfers are free. This is such an important component of good transit that it’s spreading across Europe, but Germany is the origin, and this is really part of the coordination of planning between U- and S-Bahn service.
Zonal fares: fares are in zones, rather than depending more granularly on distance as is common in Asia. Zones can be concentric and highly non-granular as in Berlin, concentric and granular as in Munich, or non-concentric as in Zurich.
Monthly and annual discounts: there is a large discount for unlimited monthly tickets, in order to encourage people to prepay and not forget the fare when they ride the train. There are even annual tickets, with further discounts.
No smartcards: the German-speaking world has resisted the nearly global trend of smartcards. Passengers can use paper tickets, or pay by app. This feature, unlike many others, has not really been exported – proof-of-payment is common enough in much of Northern and Central Europe, but there is a smartcard and the fare inspectors have handheld card readers.
Verkehrsverbund: the Verkehrsverbund is an association of transport operators within a region, coordinating fares first of all, and often also timetables. This way, S-Bahn services operated by DB or a concessionaire and U-Bahn and bus services operated by a municipal corporation can share revenue. The first Verkehrsverbund was Hamburg’s, set up in 1965, and now nearly all of Germany is covered by Verkehrsverbünde. This concept has spread as a matter of fare integration and coordinated planning, and now Paris and Lyon have such bodies as well, as does Stockholm.
Germany has no head
The American, Soviet, British, and French traditions all rely on exports of ideas from one head megacity: New York, Moscow, London, Paris. This is not at all true of the German tradition. Berlin was the richest German city up until World War 2, and did influence planning elsewhere, inspiring the Vienna Stadtbahn and the re-electrification of the Hamburg S-Bahn with third rail in the late 1930s. But it was never dominant; Hamburg electrified its S-Bahn 20 years earlier, and the Rhine-Ruhr region was planning express regional service connecting its main cities as early as the 1920s.
Instead, German transportation knowledge has evolved in a more polycentric fashion. Hamburg invented the Verkehrsverbund. Munich invented the postwar S-Bahn, with innovations like scheduling a clockface timetable (“Takt”) around single-track branches. Cologne and Frankfurt opened the first German Stadtbahn tunnels (Boston had done so generations earlier, but this fell out of the American planning paradigm). Karlsruhe is so identified with the tram-train that this technology is called the Karlsruhe model. Nuremberg atypically built a fully segregated U-Bahn, and even more atypically was a pioneer of driverless operations, even beating Paris to be the first city in the world to automate a previously-manual subway, doing so in 2010 vs. 2012 for Paris.
There’s even significant learning from the periphery, or at least from the periphery that Germany deigns acknowledge, that is its immediate neighbors, but not anything non-European. Plans for the Deutschlandtakt are based on the success of intercity rail takt planning in Switzerland, Austria, and the Netherlands, and aim to build the same system at grander scale in a larger country.
The same polycentric, headless geography is also apparent in intercity rail. It’s not just Germany and Switzerland that build an everywhere-to-everywhere intercity rail system, in lieu of the French focus on connecting the capital with specific secondary cities. It’s Austria too, even though Vienna is a dominant capital. For that matter, the metropolitan area of Zurich too is around a fifth of the population of Switzerland, and yet the Swiss integrated timed transfer concept is polycentric.
Does this work?
On the most ridiculously wide definition of its metropolitan area, Vienna has 3.7 million people, consisting of the city proper and of Lower Austria. In 2012, it had 922 million rail trips (source, PDF-p. 44); the weighted average work trip modal split in these two states is 40% (source, PDF-p. 39). In reality, Vienna is smaller and its modal split is higher. Zurich, an even smaller and richer city, has a 30% modal split. Mode shares in Germany are somewhat lower – nationwide Austria’s is 20%, Germany’s is 16% – but still healthy for how small German cities are. Hamburg and Stuttgart both have metropolitan public transport modal splits of 26%, and neither is a very large city – their metro areas are about 3.1 and 2.6 million, respectively. Munich is within that range as well.
In fact, in the developed world, one doesn’t really find larger modal splits than these in the 2 million size class. Stockholm is very high as well, as are 1.5th-world Prague and Budapest, but one sees certain German influences in all three, even though for the most part Stockholm is its own thing and the other two are Soviet. Significantly higher rates of public transport usage exist in very large Asian cities and in Paris, and Germany does deserve demerits for its NIMBYism, but NIMBYism is not why Munich is a smaller city than Taipei.
To the extent there’s any criticism of the German rapid transit planning tradition, it’s that construction costs lately have been high by Continental European standards, stymieing plans for needed expansion. Märkisches Viertel has been waiting for an extension of U8 for 50 years and it might finally get it this decade.
The activist sphere in Germany is especially remarkable for not caring very much about U-Bahn expansion. One occasionally finds dedicated transport activists, like Zukunft Mobilität, but the main of green urbanist activism here is bike lanes and trams. People perceive U- and S-Bahn expansion as a center-right pro-car plot to remove public transit from the streets in order to make more room for cars.
The high construction costs in Germany and the slow, NIMBY-infused process are both big drags on Germany’s ability to provide better public transportation in the future. It’s plausible that YIMBYer countries will overtake it – that Korean and Taiwanese cities of the same size as Munich and Hamburg will have higher modal splits than Munich and Hamburg thanks to better transit-oriented development. But in the present, the systems in Munich and Zurich are more or less at the technological frontier of urban public transportation for cities of their size class, and not for nothing, much of Europe is slowly Germanizing its public transport planning paradigm.
Tram-Trains
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 center | Fast in center | |
| Slow in outlying areas | Tramway | Stadtbahn |
| Fast in outlying areas | Tram-train | Rapid transit |
The terms fast and slow are again relative to general traffic. The Paris Métro averages 25 km/h, less than some mixed-traffic buses in small cities, but it still counts as fast because the speed in destinations accessed per hour is very high.
Be aware that I am using the terms Stadtbahn and tram-train to denote two different things, but in Karlsruhe the system is locally called Stadtbahn. German cities use the term Stadtbahn to mean “a tramway that doesn’t suck,” much as American cities call a dazzling variety of distinct things light rail, including lines in all four cells of the above table. Nonetheless, in this post I am keeping my terminology distinct, using the advantage of switching between different languages and dialects.
Tram-trains and regional rail
The Karlsruhe model involves trains running on mainline track alongside mainline trains, diverging to dedicated tramway tracks in the city, to connect Karlsruhe Hauptbahnhof with city center around Marktplatz. This also includes lines that do not touch the mainline, like S2, but still run with higher-quality right-of-way separation outside city center; but most lines run on mainline rail part of the way.
North American light rail lines, with the exception of the Boston, Philadelphia, and San Francisco Stadtbahn systems, tend to run as tram-trains, but never have this regional rail tie-in. They run on entirely dedicated tracks, which has two important effects, both negative. First, it increases construction costs. And second, it means that the shape of the network is much more a skeletal tramway map than the more complicated combination of an S-Bahn and a tramway that one sees in Karlsruhe. San Diego has a short segment sharing tracks with freight with time separation, but the shape of the network isn’t any different from that of other American post-1970s light rail systems, and there’s an ongoing extension parallel to a mainline railroad that nonetheless constructs a new right-of-way.
In this sense, the Karlsruhe model can be likened to a cheaper S-Bahn. S-Bahn systems carve new right-of-way under city center to provide through-service whenever the historic city station is a terminus, such as in Frankfurt, Stuttgart, Munich, or German-inspired Philadelphia. They can also build new lines for more expansive service, higher capacity, or a better connection to city center, like the second S-Bahn trunk in Hamburg; Karlsruhe itself is building a combined road and rail tunnel, the Kombilösung, after a generation of at-grade operation. The tram-train is then a way to achieve some of the same desirable attributes but without spending money on a tunnel.
It follows that the tram-train is best when it can run on actual regional rail tracks, with good integration with the mainline system. It is a lower-speed, lower-cost version of a regional rail tunnel, whereas the North American version running on dedicated tracks is a lower-cost version of a subway. Note also that regional rail can be run at different scales, the shorter and higher-frequency end deserving the moniker S-Bahn; the Karlsruhe version is long-range, with S1 and S11 reaching 30 km south of city center and S5 reaching 70 km east.
Where is a tram-train appropriate?
Jarrett’s 2009 post lays down three criteria for when tram-trains work:
- The travel market must be small enough that an S-Bahn tunnel is not justified.
- The destination to be served isn’t right next to the rail mainline.
- The destination to be served away from the mainline is so dominant that it’s worthwhile running at tramway speeds just to get there and there aren’t too many people riding the line beyond it.
The center of Karlsruhe satisfies the second and third criteria. It is borderline for the first – the region has maybe a million people, depending on definitions, and the city proper has 312,000 people; the Kombilösung is only under-construction now and was not built generations ago, unlike S-Bahn tunnels in larger cities like Munich.
Jarrett points out that in the urban world he’s most familiar with, consisting of the United States, Canada, Australia, and New Zealand, it is not common for cities to satisfy these criteria. He does list exceptions, for example Long Beach, where the Blue Line runs in tramway mode before heading into Los Angeles on a mostly grade-separated right-of-way, whereupon it goes back into the surface in Downtown LA before heading into an under-construction tunnel. But overall, this is not common. City centers tend to be near the train station, and in the United States there’s such job sprawl that just serving one downtown destination is not good enough.
That said, the Long Beach example is instructive, because it is not the primary city in its region – Los Angeles is. I went over the issue of outlying S-Bahn tunnels a year ago, specifying some places where they are appropriate in Israel. The tram-train must be a key tool in the planner’s box as a cheaper, lower-capacity, lower-speed version of the same concept, diverging from the mainline in tramway mode in order to serve a secondary center. Karlsruhe itself is a primary urban center – the only time it’s the secondary node is when it connects to Mannheim, and that train doesn’t use the tramway tracks – but a secondary tram-train connection is being built in outlying areas there, namely Heilbronn.
Different models of urban geography
In the American model of urban geography, cities are contiguous blobs. Stare at, for example, Chicago – you’ll see an enormous blob of gray stretching in all directions. Parkland is mostly patches of green in between the gray, or sometimes wedges of green alternating with wedges of gray, the gray following commuter railroads and the green lying in between. Boundaries between municipalities look completely arbitrary on a satellite map.
In the German model of urban geography, it’s different. Look at Cologne, Frankfurt, Mannheim, or Stuttgart – the built-up area is surrounded by green, and then there are various suburban towns with parkland or farmland in between. This goes even beyond the greenbelt around London – there’s real effort at keeping all these municipalities distinct.
I don’t want to give the impression that the United States is the weird one. The contiguous model in the United States is also common in France – Ile-de-France is one contiguous built-up area. That’s how despite being clearly a smaller metropolitan region than London, Paris has the larger contiguous population – see here, WUP 2007, and see also how small the German and Dutch urban areas look on that table. Urban agglomeration in democratic East Asia is contiguous as in the US and France. Canada looks rather American to me too, especially Vancouver, the city both Jarrett and I are the most familiar with, while Toronto has a greenbelt.
This distinction moreover has to be viewed as a spectrum rather than as absolutes. Boston, for example, has some of the German model in it – there’s continuous urbanization with inner suburbs like Cambridge and Newton, but beyond Route 128, there are many small secondary cities with low density between them and the primary center. Conversely, Berlin is mostly American or French; the few suburbs it has outside city limits are mostly contiguous with the city’s built-up area, with the major exception of Potsdam.
The relevance of this distinction is that in the German or Dutch model of urban geography, it’s likely that a railway will pass through a small city rather far from its center, fulfilling the second criterion in Jarrett’s post. Moreover, this model of independent podlike cities means that there is likely to be a significant core, which fulfills the third criterion. The first criterion is fulfilled whenever this is not the center of a large metropolitan area.
It’s not surprising, then, that the Karlsruhe model has spread to the Netherlands. This is not a matter of similarity in transport models: the Netherlands differs from the German-speaking world, for examples it does not have monocentric S-Bahns or S-Bahn tunnels and it builds train stations with bike parking where Germany lets people bring bikes on trains. Nonetheless, the shared model of distinct municipalities makes tram-train technology attractive in South Holland.
Israel and tram-trains
In Israel, there are very few historic railways. A large share of construction is new, and therefore has to either swerve around cities or tunnel to enter them, or in a handful of cases run on elevated alignments. Israel Railways and local NIMBYs have generally preferred swerving.
Moreover, the urban layout in Israel is very podlike. There do exist contiguous areas of adjacent cities; Tel Aviv in particular forms a single blob of gray with Ramat Gan, Givatayim, Bni Brak, Petah Tikva, Bat Yam, and Holon, with a total population of 1.5 million. But for the most part, adjacent cities are buffered with undeveloped areas, and the cities jealously fight to stay this way despite extensive developer pressure.
The final important piece in Israel’s situation is that despite considerable population growth, there is very little rail-adjacent transit-oriented development. The railway was an afterthought until the Ayalon Railway opened in 1993, and even then it took until last decade for mainline rail to be a significant regional mode of transport. The state aggressively builds new pod-towns without any attempt to expand existing towns toward the railway.
The upshot is that all three of Jarrett’s criteria for tram-trains are satisfied in Israel, everywhere except in and around Tel Aviv. Tel Aviv is large enough for a fully grade-separated route, i.e. the already-existing Ayalon Railway. Moreover, because Tel Aviv needs full-size trains, anything that is planned to run through to Tel Aviv, even as far as Netanya and Ashdod, has to be rapid transit, using short tunnels and els to reach city centers where needed. A tram-train through Ashdod may look like a prudent investment, but if the result is that it feeds a 45 meter long light rail vehicle through the Ayalon Railway then it’s a waste of precious capacity.
But Outside Tel Aviv, the case for tram-trains is strong. One of my mutuals on Twitter brings up the Beer Sheva region as an example. The mainline going north has a station called Lehavim-Rahat, vaguely tangent to Lehavim, a ways away from Rahat. It could get two tramway branches, one diverging to the built-up area of Lehavim, a small suburb that is one of Israel’s richest municipalities, and the other to Rahat, one of Israel’s poorest. There are also interesting options of divergence going south and east, but they suffer from being so far from the mainline the network would look scarcely different from an ordinary tramway.
Beer Sheva itself would benefit from tramways with train through-service as well. The commercial center of the city is close to the train station, but the university and the hospital aren’t, and are not even that close to the subsidiary Beer Sheva North station. The station is also awkwardly off-center, lying southeast of the city’s geographic center, which means that feeding buses into it with timed transfers screws internal connections. So tramway tracks on Rager Boulevard, cutting off Beer Sheva North for regional trains, would do a lot to improve regional connectivity in Beer Sheva; intercity trains should naturally keep using the existing line.
In the North, there are similar examples. Haifa is not going to need the capacity of full-size trains anytime soon, which makes the case for various branches diverging into smaller cities to provide closer service in tramway mode strong. Unlike in Beer Sheva, the case for doing so in the primary center is weak. Haifa’s topography is the stuff of nightmares, up a steep hill with switchback streets. The mainline already serves the Lower City well, and climbing the hill is not possible.
This creates an interesting situation, in which the technology of the tram-train in the North can be used to serve secondary cities like Kiryat Ata and Tirat Carmel and maybe enter the Old City of Acre, but the operational pattern is really that of a Stadtbahn – fast through Haifa and up most of the Krayot, slow through smaller suburbs.
Stadtbahn Systems
I made an off-hand remark about subway-surface systems, called Stadtbahn in German (as is, confusingly, the fully grade-separated east-west Berlin S-Bahn line), regarding a small three-line single-tail network that Brooklyn could build. I also talked about it in a little more detail last year. I want to go more deeply into this now. It’s a public transportation typology that’s almost nonexistent outside Germany and Belgium; Tel Aviv is building one line, and the US has three but two of those are from more than 100 years ago. But there are interesting examples of good places to use this technology elsewhere, especially elsewhere in Europe.
What is the Stadtbahn?
The Stadtbahn (“city rail”), or the subway-surface line in US usage, is an urban line running light rail vehicles, with grade separation in city center and street running outside city center. All examples I know of are in fact underground in city center, but elevated lines or lines running in private rights-of-way could qualify too, and in Cologne, there’s a semi-example over a bridge dropping to the surface at both ends.
It’s best illustrated as a 2*2 grid:
| Slow in center | Fast in center | |
| Slow in outlying areas | Tramway | Stadtbahn |
| Fast in outlying areas | Tram-train | Rapid transit |
The terms fast and slow are relative to general traffic, so a mixed-traffic bus in a low-density city that averages 30 km/h is slow whereas the Paris Métro, which averages 25 km/h, is fast; the speed in km/h may be higher on the bus, but the speed in destinations accessed per hour is incomparably higher on the Métro.
The tram-train is confusingly also called Stadtbahn in Germany, for example in Karlsruhe; this is nearly every light rail built in North America. It is not the topic of this post.
What is the purpose of the Stadtbahn?
Historically, Stadtbahn systems evolved out of pure surface tramways. City center congestion made the streetcars too slow, so transit agencies put the most congested segments underground. This goes back to Boston in 1897 with the Tremont Street Subway and Philadelphia in 1906 with the Subway-Surface Lines. The contrast both in that era and in the era of Stadtbahn construction in Germany from the 1960s to the 80s is with pure subways, which are faster but cost more because the entire route must be underground.
Stadtbahns always employ surface branching. This is for two reasons. First, there’s more capacity underground than on the surface, so the higher-capacity rapid transit segment branches to multiple lower-capacity tramways to permit high throughput. And second, there’s generally less demand on the outer segments than in the center – lines with very strong demand all the way tend to turn into full subways.
This is therefore especially useful for cities that are not huge. In a city the size of Cologne or Stuttgart or Hanover, there isn’t and will never be demand for a rapid transit system with good citywide coverage. Instead, there is something like a sector principle. For example, in Cologne, the Deutz side of the city, on the right bank of the Rhine, has service to city center on the S-Bahn, on tramway lines over the Deutzer Bridge branching on the surface, and on tramway lines over the Mülheimer and Severin Bridges feeding into the north-south ring Stadtbahn. Smaller cities have simpler systems – Hanover for has three underground trunk lines meeting at one central station, and Dortmund has three meeting in a Soviet triangle. This maintains good coverage even without the budget for many rapid transit lines.
Where are Stadtbahns appropriate?
Cities should consider this technology in the following cases:
- The city should not be too big. Tel Aviv is too big for this, and people in Israel are starting to recognize this fact and, in addition to the under-construction three-line Stadtbahn system are proposing a larger-scale three-line fully grade-separated metro system. If the city is big enough, then a full metro system is justified.
- There should be a definitive city center for substantial traffic to funnel to. The purpose of the Stadtbahn is to have comparable throughput to that of a metro, albeit with shorter trains.
- There should be wide swaths of sectors of the city where having multiple parallel lines is valuable. This, for example, is the case in cities that are not exceptionally dense and cannot expect transit-oriented development to completely saturate one metro corridor.
- The street network should not be too gridded, because then the sector-based branching is more awkward, and the combination of rapid transit to city center and a surface transit grid can be powerful, as in Toronto.
- There should be too much city center congestion for a pure surface system to work, for example if most streets are very narrow and traffic funnels to the few streets that can use
These circumstances are all common to German urbanism: city centers here are strong, but residential density peaks at 15,000/km^2 or thereabouts in near-center neighborhoods and drops to 3,000-6,000/km^2 farther out. Moreover, Germany lacks huge cities, and of the largest four urban cores – Berlin, Hamburg, Munich, Frankfurt – three have full rapid transit systems. Finally, grids are absent here except at very small scale, as in Mannheim.
However, these are not unique features to Germany. They’re common around Europe. European cities are not very big, and the only ones that can genuinely fill any subway line with transit-oriented development are a handful of very big, very rich ones like London and Paris. Even Stockholm and Munich have to be parsimonious; they have have full metro systems with branching.
The French way of building rapid transit does not employ the Stadtbahn, and perhaps it should. In a city the size of Bordeaux or Nice, putting a tramway underground in city center and then constructing new branches to expand access would improve coverage a lot.
This is likely also the case in Italian cities below the size class of Milan or Rome. Many of these cities are centered around Renaissance cores with very narrow streets, which are nonetheless auto-centric with impossibly narrow sidewalks, Italy having nearly the highest car ownership in Europe. Finding one to three good corridors for a subway and then constructing tramways funneling into them would do a lot to speed up public transit in those cities. Bologna, for example, is planning a pure surface tramway, but grade-separated construction in the historic center would permit trams to have decent coverage there without having to slow down to walking speed.
Are there good examples outside Europe?
Yes! From my original post from 2016, here is one proposal for New York:
The B41 could be a tramway going between City Hall and Kings Plaza, using two dedicated lanes of the Brooklyn Bridge. In that case, the line would effectively act as subway-surface, or more accurately elevated-surface: a surface segment in Brooklyn, a grade-separated segment between Manhattan and Brooklyn. Subway-surface lines should branch, as all current examples do (e.g. Boston Green Line, Muni Metro, Frankfurt U-Bahn), because the subway component has much higher capacity than the surface components. This suggests one or two additional routes in Brooklyn, which do not have strong buses, but may turn into strong tramways because of the fast connection across the river to Manhattan. The first is toward Red Hook, which is not served by the subway and cut off from the rest of the city by the Gowanus Expressway. Unfortunately, there is no really strong corridor for it – the streets are not very wide, and the best for intermediate ridership in Cobble Hill and Carroll Gardens require additional twists to get into the core of Red Hook. Court Street might be the best compromise, but is annoyingly a block away from the F/G trains, almost but not quite meeting for a transfer. The second possible route is along Flushing Avenue toward the Navy Yard; it’s not a strong bus by itself, but the possibility of direct service to Manhattan, if a Flatbush tramway preexists, may justify it.
Note that this proposal is opportunistic: Brooklyn Bridge just happens to be there and point in the right direction for at least one strong surface route in Brooklyn, and conversely would connect too awkwardly to the subway. In a city the size of New York, Stadtbahn lines must be opportunistic – if the region intentionally builds new river crossings then they must carry the highest-capacity mode of transportation, which is rapid transit, not a light rail variant.
American cities smaller than New York are often very big by European standards, but also very decentralized. This hurts the Stadtbahn as a mode – it really only works for a monocentric city, because if there are multiple centers, then all but the primary one get slow transit. The Rhine-Ruhr notably uses the S-Bahn, which is rapid transit, to connect its various cities, and only run Stadtbahn service internally to each center, like Cologne or Dortmund.
There are a number of places in the United States where burying a light rail line in city center is advisable, but this is for the most part conversion of a tram-train to rapid transit, for examples in Portland and Dallas. The only example that come to mind of a decent Stadtbahn in the US that doesn’t already exist is Pittsburgh, converting the BRT system to rail.
Outside the United States, I get less certain. Canada is bad geography for a Stadtbahn because of its use of grid networks; Ottawa may be good for a Stadtbahn using the Confederation Line tunnel, but that’s probably it. Australia may be better, combining decently strong city centers with very low residential density; transit-oriented development potential there is very high, but it could plausibly come around multiple distinct corridors as well as regional rail stations. Melbourne’s tramways thus may be a candidate for Stadtbahn conversion.
In both East Asia and in the developing world, it’s likely best to just build full metros. East Asian cities are big and have high rates of housing construction (except Hong Kong). I can see a Stadtbahn succeed in Taichung, extending the under-construction Green Line on the surface and building intersecting lines, but that’s probably it. Kaohsiung already has a (very underused) subway, what I think is Daejeon’s best next corridor on top of Line 1 and the planned Line 2 is unusually bad for a Stadtbahn because the streets are too gridded west of the center, Daegu is too gridded as well.
A similar set of drawbacks is also true for the developing world. The urban population of the developing world tends to cluster in huge cities. Moreover, these cities tend to have high residential density but low city center job concentration; the Addis Ababa light rail is bad at serving people’s work trips because so few people work in the center. Finally, the developing world has high rates of increase in urbanization, which make future-proofing systems with higher capacity more valuable.
Pedestrian Observations 
