All construction cost figures that I sign my name to adjust currencies for purchasing power parity, or PPP. In other words, I convert currencies across countries in PPP terms, not exchange rate terms. This is not how everyone else does this; the World Bank analysis of global high-speed rail costs converts currencies by exchange rate, and, since the yuan is undervalued, concludes Chinese construction costs are below world average, whereas in fact they are above average.
Because nearly all of the costs of the construction of infrastructure are local. Labor is almost entirely local, and materials are as well, since concrete is made locally rather than imported. Foreign expertise and machinery are internationally traded; in those cases, currency devaluations can lead to cost overruns, but the proportion of the cost that is traded remains low.
India: an indigenization plan from the 2000s was quoted as reducing costs by 10-15%. The rupee’s exchange rate value is lower than its PPP value by a factor of about 3.3; indigenization reducing costs by 10-15% is compatible with around 20% of the total value of the original contract being imported.
Philippines: I spoke with a DOTR planner, who said that 90% of the value of civil works is local, and only 10% is imported, such as foreign expertise and imported material; the planner said that rolling stock is imported, but our construction cost estimates exclude rolling stock when possible.
Why not wages?
Because while the bulk of costs are domestic, they are not labor in developing countries. In Turkey, which is not much poorer than Southern Europe, costs split as 20% labor (US: 55%), 40% permanent materials, 10% construction materials, 30% construction equipment. The 80% non-labor costs are mostly domestically-produced, at local wages, but also at local productivity. If Turkey could produce everything at the same productivity as a richer country, it would just be a richer country. This goes even more so for actually poor countries like India and the Philippines.
The impact of PPP
With PPP adjustment, GDP per capita ceases to be a significant correlate of construction cost per km, except through the tendency of poor countries to build more elevated and fewer subway lines. This was not the original intention of the adjustment, which was to smooth dollar-euro difference, but it’s suggestive that it’s correct and meaningful.
I recently found two presentations, one from 2017, the other from earlier this week, both underscoring the importance of in-house expertise for efficient construction. This is layered on top of interviews Eric and I did for our Boston case study and a few additional interviews I did in other American and European cities. It is my professional opinion that agencies that engage in major capital projects, even if they involve rolling stock acquisition rather than the construction of new lines, ought to hire in-house, and make sure to have long-term capital programs.
Both presentations concern rolling stock. The one from 2017 is by Stadler, regarding the challenges of the American market. On slide 32, it mentions that Caltrain was a demanding customer, with all expertise outsourced and yet managers engaging in micromanagement. The micromanagement is in line with what we’ve heard from contractors for other capital expansions, like Second Avenue Subway, especially contractors with experience in both the US, where this practice is common, and Europe, where it isn’t.
Thanks to the factors mentioned by Stadler as well as the Buy America requirement to set up a new factory with a new supply chain for a midsize order, the cost is $551 million/96 cars, or $5.74 million/car; the typical cost of a KISS is 300 million €/90 cars, and the €:$ ratio is not 1.72, far from it.
The other presentation, from this week, concerns the MBTA’s slow approach to electrifying its commuter rail network. It wishes to begin with a pilot on the already-electrified Providence Line, but is running against the problem of having no in-house expertise, just as Caltrain does not. The presentation on this says, on slide 3, that it takes 6-9 months to onboard consultants, and another 6-9 to develop performance requirements for a kind of vehicle that is completely standard in high-performance regional rail networks in Europe.
Instead of hiring experienced professionals (who must come from Europe or East Asia and not the US), the MBTA plans to piggyback on either the overpriced Caltrain order, or an obsolete-technology order by New Jersey Transit. The Caltrain order, moreover, is stretched for the generous loading gauge of the Western US, but does not fit the catenary height on the East Coast, even though European KISSes would easily and are around 13 cm lower than existing MBTA rolling stock.
Prior Northeastern examples
This combination of political and managerial micromanagement with outsourcing of technical expertise to consultants is common enough in the United States. In the Boston report on the Green Line Extension, we were told by multiple sources that the MBTA only has 5-6 engineers doing design review. Thus, they have the capacity to handle small projects but not large ones.
Small-scale projects like building a new infill station or taking an existing low-platform commuter rail station and converting it to an accessible high-platform one usually have limited cost premium: in Berlin, infill stations are 10 million € outside the Ring, whereas in Boston, infill stations and high-platforming projects (which are very similar in scope) are around $20-25 million – and Boston platforms are longer. This is also the case in Philadelphia, where headline costs are lower because the stations are smaller, but overall the unit costs are comparable to those of Boston.
But large projects are beyond the ability of a 6-person team. The required permanent staffing level is likely in the teens for a team whose job is just to score design and construction contracts. This choked the original Green Line Extension, leading to bottlenecks in design and contributing to the project’s extreme cost. The restarted version is still extremely expensive – it’s getting some good press this week for running slightly under a $2.3 billion/6.3 km budget, but said budget, $360 million/km, is well above the international norm for a subway, let alone trenched light rail. The current project has sunk costs from the previous ones, and a combination of in-house and consultant design about whose efficacy we’ve heard conflicting reports, but the team is much larger now.
In areas that don’t even have the skeletal design review staff of Boston, costs are high even for small projects. Connecticut deserves especial demerit: its department of transportation relies exclusively on consultants for rail design (perhaps also road design but I do not know), and infill stations cost not $20-25 million but $50+ million. The Hartford Line, compromised from the start, even displays this state-by-state difference: the one Massachusetts project, a single high platform in Springfield, cost $10 million/100 meters, a fraction of comparable projects in Connecticut. Larger Connecticut stations, such as those for Metro-North, have seen extreme scope creep, amounting to a $106 million total cost.
Consultants and design
American agencies speak of design-bid-build contracts, in which design and construction are separate, and design-build ones, where they are combined into a single contract. Design-bid-build is superior. But really, contracts in low-cost countries are often neither of those, but just build contracts, with design done mostly in-house. A procurement official in Stockholm explained to me that Swedish contracts tend to be build contracts; design-bid-build can sometimes be used with supplemental consultants helping with design, but it’s not the norm. Moreover, in Oslo, the use of design consultants instead of in-house design has not been good: consultants tend to engage in defensive design because of how Norway structures risk allocation, leading to overbuilding.
In Spain and (I believe) Italy, contracts are design-bid-build. But there’s so much in-house involvement in design that it’s more accurate to call these build contracts. The in-house design teams are not huge but they’re enough to work with private design firms and score proposals for technical merit. In Istanbul, the system is somewhat different: preliminary design at the 60% level is contracted out separately from the combination of final design and construction, which may possibly be called des-bid-ign-build, but the design part is extensively scored on technical merit, at 60-80% of the total weight. The construction contracts in Istanbul are lowest-bid, but contractors can be disqualified, and since Turkey has so much infrastructure construction, contractors know that they need to behave well to get future work.
Unfortunately, American consultants believe the opposite: they believe in the superiority of design-build and are not even aware of pure build, only design-bid-build. Sources from that world that I generally think highly of have told me that directly. But that is because the sort of projects that they are most likely to be involved in are ones that use consultants, which definitionally are not build contracts. The ongoing expansion projects in Stockholm, Madrid, Barcelona, Milan, Rome, and Berlin have no use for international consultants, so international consultants are not familiar with them, and end up knowing only about high-cost examples like London or the occasional medium-cost one like Paris. In effect, to rely on consultants is to ascertain one largely learns worst industry practices, not best ones.
The alternative to paying consultants is to obtain public-sector expertise. Agencies are obligated to hire sufficient-size teams, and pay them competitively. Engineers in Italy and Spain have a lot of social prestige, much as in France and Germany; even in medium- rather than low-cost countries in Europe, like France, we were told by UITP planners that the people planning metro systems are hired from the engineering elite (in France, this would be Grandes Ecoles graduates), and paid appropriately.
In the US, there is no such prestige. Humanities professors speak of STEM privilege routinely, but by Continental and East Asian standards, the US and UK have no STEM privilege: the elites are generalist and are not expected to know the specific industrial fields they oversee. The public sector thus treats the planner and the engineer as a servant to the political appointee. Senior management routinely ignores the advice of younger planners who are more familiar with present-day research.
The pay, too, is deficient. In absolute numbers, planners at American transit agencies get paid better than their European counterparts – but American white-collar wages are generally higher than European ones. The MBTA pays project managers $106,000 a year as of a few years ago, which is a nice wage, but the Boston private sector pays $140,000 in transportation and more in other fields. The public sector, through budget-cutting officials, sends a clear price signal: we do not want you to work for us.
There is another way, but it requires letting go of the idea that private consultants are better than long-term in-house experts. It is obligatory to hire in-house at competitive wages to grow the design review teams, and listen to them when they say something is desirable, difficult, or impossible. Instead of onboarding consultants, agencies should immediately staff up in-house with plans for long-term investments. Moreover, senior management should back the planners and engineers when they engage in value engineering, even if it annoys politicians and local activists. The role of elected politicians is to review those in-house plans and decide whether there is room in the budget for the megaprojects they recommend, and not to micromanage. This way, and only this way, can the United States shrink its procurement costs to typical Continental European levels.
Separately, because of Noah Smith’s opinions about high-speed rail, today there is going to be an event featuring me and him in which we are going to discuss the issue in an American context, alongside a presentation of the database and what lessons can be drawn from it. You can register here; it’s at 13:00 Eastern US Time, or 19:00 Berlin time.
A few notes regarding our database, because I’m being asked on Twitter, and also because it’s relevant for our research:
This is a well-studied topic
Literature on comparative HSR costs already exists, and some of our internal cost references are to studies on the subject. This is not like subway costs, where the biggest databases I know of prior to ours are a Flyvbjerg paper and a Spanish analysis each with a number of items in the teens. This should not in a way be surprising: the costs and impact of megaprojects are analyzed more than those of smaller projects, and subways are megaprojects of greater size than surface transit or street reconstruction but HSR is of yet greater size. Thus, subways are significant enough that we have been able to find largely complete costs from trade and mass media and government reports, which task is far harder for bus lanes or bike lanes, whereas with HSR, not only is it possible to find complete costs, but also there is extensive public debate and analysis.
I believe our contribution to the discussion, then, is not the database itself, but two new points:
- Contrary to the World Bank report on the subject (see here, starting printed page 39), China does not build HSR especially cheaply. Our findings are not too different from the World Bank’s for lines built up to the publication of the report measured in yuan per km, but we adjust for PPP and therefore the cost in dollars per km is higher, and, moreover, the more recent lines appear to be more expensive. In fact, Chinese costs are higher than European ones. The reason is that China builds its HSR almost entirely on viaduct, whereas in Europe, viaducts are rare, and segments that are not in tunnel are built at-grade or on earthworks.
- There is positive correlation between a country’s HSR costs per km, net of tunnels, and its subway construction costs. This is not perfect correlation, but one can see Britain, the Netherlands, and Taiwan perform poorly in both areas. France and Germany are in the middle. Spain is very cheap. The exceptions are notable: Italy has cheap subways and expensive HSR, which Paolo Beria, author of one of our source papers, attributes to overbuilding and overdesign, with extensive tunnels and freight-friendly grades.
We only include under-construction or open lines
This contrasts with lines that are only in early design and may not yet have a cost – for example, Frankfurt-Mannheim will only publish its cost estimate next year, in a parliamentary budget setting in order to decide whether to proceed (for which the answer is certainly yes, as the benefits to the network are intensive). This also contrasts with canceled and indefinitely postponed lines, such as California High-Speed Rail and the Portuguese lines killed during the Great Recession’s austerity. Canceled lines are upward-biased: the state is likelier to cancel or choose not to build a line if it is more expensive than the average, as we can readily see with California, and therefore we do not wish to compare built with unbuilt lines.
The above analysis is equally true of our subway construction costs database – if a line is canceled, it is purged, even if design or even physical construction began. Gateway for example is under active design and engineering and is therefore included, even if they are still seeking funding, but if it is canceled it will be purged (but if it is rebooted, as I hope, then the sunk cost will be included, as with the Green Line Extension in Boston).
The difference is that our HSR cost database is more historic. It is close to complete for France, Germany, Italy, Spain, Belgium, and Korea, and complete for single-line Taiwan and the Netherlands and for the UK. This is because it’s just easier to find historic data for HSR than for subways, where I wish I could get a complete historic series for big cities with big systems like Paris, Madrid, and Berlin, but can’t even find 1970s-80s costs for any of them. Conversely, ongoing projects make it surprisingly difficult at times to find tunnel and viaduct percentages, and the escape path of going on Google Earth and OpenStreetMaps and measuring is not available.
What is included?
As far as possible, costs are for civil infrastructure, systems, stations, and overheads, but not rolling stock or financing charges. Austria’s Koralmbahn has two sets of numbers, differing by a factor of 2, with one source claiming that it is about whether financing is included. It is my belief that, owing to the high profitability of HSR if cost of capital is ignored, it is best to think in terms of returns on investment and not try to incorporate debt or finance charges into the actual cost.
The importance of avoiding viaducts and tunnels
The Asian tendency to build on viaduct where the line is not in tunnel leads to high costs. Likewise, the use of shallow grades and low superelevation for mixed lines or even for some dedicated lines (the Shinkansen, without any track sharing, hews to 1.5% grads) raises construction costs.
Netting out tunnels is still useful when trying to figure out itemized costs and cost control that is not about what to build, for example about labor or procurement. It is also useful when comparing lines in the mountainous terrain of Austria, Japan, Korea, and Switzerland to the easier North European Plain. But at some point, it is necessary to treat the tunnel percentage as endogenous to the planning system. The viaduct percentage, moreover, is absolutely endogenous.
France in this context does well by keeping lines at grade as much as possible. The only country with less tunneling than France is Morocco, which builds its urban and high-speed trains as if it were France, and, thanks to France’s extensive presence in the Maghreb, French contractors are intimately familiar with the local situation and build cheaply. France and Germany have similar unit costs, but Germany tunnels a lot more, less because of the terrain and more because of either politics (that is, the Erfurt detour for Berlin-Munich, forcing the line to go through thicker mountains) or a misguided attempt at building mixed lines in the 1980s and 90s.
The United States’ high projected budgets for proposed lines that never go anywhere thanks to their extreme costs come from overbuilding more than high unit prices. For example, in Baltimore, a two-track tunnel project designed for exclusive electric passenger train usage turned into a four-track tunnel with enough room for double-stacked freight with mechanical ventilation for diesel locomotives. The scope creep raised the projected budget from $750 million in the late 2000s to $4 billion in the mid-2010s.
There’s a report just released by the Grattan Institute called Megabang for Megabucks, talking about high construction costs in Australia. Our transit costs project is quoted as an international comparison, pointing out that Australia is near the global high end. I encourage people to read the report itself, which says interesting things about problems with Australian construction and procurement. I am especially happy to see that the recommendations for the most part accord with what we are learning from other cases – of course, our Boston case is out and the report authors have likely read it, but the recommendations are in line with things we see from yet-unpublished cases, so this is not just me looking at a mirror.
The issue of competition
Australian megaproject contracts have insufficient competition. Only three firms are Tier One, the largest infrastructure contractors in Australia; those get most contracts for the largest infrastructure projects, and when mid-tier firms bid, it’s often in partnership with a Tier One company. Moreover, in the largest size category, higher than $1 billion, even the Tier One firms often partner with one another, leading to monopoly.
International firms do access the Australian market, but it is inconsistent. Australia overweights the importance of local experience, and has some unusual rules, such as requiring firms to engage in more prior design than is typical.
This is consistent with what I’ve seen in Israel. In short, the electrification contract in Israel was won by Spanish contractor SEMI, which had extensive European experience but none in Israel. This was criticized domestically, and some people blamed it for the schedule slips on the electrification project, but such blame is unfair. The bulk of the delays are not the fault of SEMI but come from a lawsuit launched by Alstom, which competed for the contract and lost out on price; Alston employed industrial espionage to create FUD about the bid, and the lawsuit delayed works by three years. Despite this, the costs have not run over much, and the absolute per-km costs remain on the low side, net of extras like Haifa’s demand for a trench. Thus, even in a situation of extensive domestic complaints about the winning bidder’s lack of local experience, said lack did not materially create problems.
This is also consistent with lessons from Turkey. In Turkey, there must be a minimum of three bidders. If there are only one or two, the state or municipal government must rebid. Absolute costs in Turkey are low and so are cost overruns; the extensive competition helps discipline the contractors, as does the political consensus in favor of rapid infrastructure construction, credibly promising firms that there will be more work in the future and if they behave they will get some of it.
The study discusses different contracting regimes. It does not talk about the design-build issue; I do not know whether it is as prevalent in Australia as in Canada, and regrettably there is no cost history, thus no way for me to confirm my suspicion that Australia resembles Canada and Singapore in only having had a cost explosion in the last 20 years. However, it does talk about change orders.
Change orders are a notable problem in California. Low bids followed by renegotiation are common there; Tutor Perini is notorious for this behavior. The study goes over strategies to deal with this issue, though it does not talk explicitly about itemization as in Spain and Italy, where the unit prices are public and then if more is needed (e.g. more labor due to slower progress) then the change is already pre-agreed, avoiding litigation. Sweden avoids litigation as well.
Finally, the study talks about rushing. This was an issue in Boston, so this may be me learning from a mirror, but, in brief, American funding for infrastructure encourages agencies to rush the preliminary design to apply for federal funding early. This leads to compromised designs and premature commitment, since there is no ongoing funding for long-term design.
Learning from good examples
I think the one drawback of the study is the list of comparisons. Sourced partly to us and partly to Read-Efron, they say,
The empirical evidence is incomplete, but what there is shows that rail construction costs in Australia are in the top quarter of 27 OECD countries studied. They are higher than in numerous other rich countries: 26 per cent higher than in Canada, 29 per cent higher than in Japan, and more than three times as high as in Spain (Figure 1.2 on the following page). And road and rail tunnels cost more in Australia than elsewhere in the world, according to an international study.
The comparison with Canada has a problem: the Canadian costs in our database go back 15-20 years, and back then, costs were much lower than today. The latest costs do not show an Australian premium over Canada – Toronto is more expensive to build in than Sydney and almost as much as Melbourne. It is critical to understand that high costs are really a pan-Anglosphere phenomenon, and thus Australia should learn from Continental European and East Asian examples (except very high-cost Hong Kong), and not from countries that in the last 10 years have had the same problems as Australia or worse. Spain is always good, as are common features to low-cost Spain, Italy, Turkey, South Korea, and the Nordic countries, and even common features to those and medium-cost countries like France, Germany, China, and Japan.
There was a conference I got invited to, consisting of three talks, two about state capacity by me and by Tyler Cowen, and one by a Canadian extramural Conservative politician named Ginny Roth (she’s a columnist but her talk was about how Conservatives could use the insights of state capacity to win elections, hence my appellation). It was run by entrepreneurs named Chris and Matt Spoke, doing a series of online meetings trying to introduce fresh ideas to what they hope will be the next crop of Tory leaders; there’s going to be one on housing in the future, and the YIMBY comments I made seemed popular with the crowd.
Here is a link to my slides. They shouldn’t be too surprising given my usual talk on construction costs and what I said before about the growth in Canadian costs. But I made sure to put the increase in costs in Canada all together in two slides, one about Toronto, sourced to Stephen Wickens, and one about the rest of Canada, sourced to both our database and to a comparison of Calgary’s costs through the 2000s with Calgary’s West LRT costs.
The organizers are in Toronto, so I didn’t talk too much about the situation in Vancouver. I said a few sentences about how I can see there was a real increase in costs from a difference between the half-elevated Canada Line and the 87% underground Broadway subway under construction, but I didn’t go into the history of the Canada Line’s cut-and-cover method or the cost estimates from the early 2010s, which had the Broadway subway costing C$250 million/km. I talked more about Toronto, where the increase in costs is larger; Vancouver, even with the cost increases, remains North America’s lowest-construction-cost city, since the other cities have had even bigger increases, including Toronto, Los Angeles, and Seattle.
I want to highlight, as I brought up 1.5 years ago, that while Canada has American (i.e. bad) mainline rail, and Americanizing construction costs, it is YIMBYer than both the US and Europe. I worry it won’t last for long, because the style of Canadian redevelopment is at fairly small radius from an arterial or a subway station and those will eventually run out, forcing upzoning of large swaths of single-family land for the benefit of everyone except the handful of aggrieved homeowners who dominate municipal politics. (There was not enough time to talk about the importance of high-level decisionmaking, that is at the provincial level and not the municipal one.)
I streamed my thoughts about the Biden infrastructure plan, and unlike previous streams, I uploaded this to YouTube. I go into more details (and more tangents) on video, but, some key points:
- Out of the nearly $600 billion in the current proposal that is to be spent on transportation, public transportation is only $190 billion: $80 billion for intercity rail, $85 billion for (other) public transit, $25 billion for zero-emissions buses. This 2:1 split between cars and transit is a change from the typical American 4:1, but in Germany it’s 55:42 and that’s with right-wing ministers of transport.
- Some of the spending on the car bucket is about electric vehicles, including $100 billion in consumer subsidies, but that’s still car spending. People who don’t drive don’t qualify for these subsidies. It’s an attempt to create political consensus by still spending on roads and not just public transit while saying that it’s green, but encouraging people to buy more cars is not particularly green, and there’s no alternative to sticks like fuel taxes in addition to carrots.
- The $25 billion for zero-emissions buses is likely to go to battery-electric buses, which are still in growing pains and don’t function well in winter. In California, in fact, trolleybuses are funded from the fixed infrastructure bucket alongside light rail and subways and are ineligible for the bucket of funding for zero-emissions buses. It is unknown whether in-motion charging qualifies for this bucket; it should, as superior technology that functions well even in places with harsh winters.
- The $85 billion for public transit splits as $55 billion for state of good repair (SOGR) and only $30 billion for expansion (including $5 billion for accessibility). This is a terrible idea: SOGR is carte blanche for agencies that aim to avoid public embarrassment rather than provide useful service to spend money without having to promise anything to show for it, and Amtrak in particular cycles between deferring maintenance and then crying poverty when money becomes available. Federal money should go to expansion alone; a state or local agency that doesn’t set aside money for maintenance now isn’t going to do so in the future, and periodic infusions of SOGR money create moral hazard by encouraging maintenance deferral in good times.
- The Amtrak money is a total waste; in particular, Amtrak wants $39 billion for the Northeast Corridor while having very little to show for it, preferring SOGR, climate resilience, and agency turf battles over the Gateway project over noticeable improvements in trip times, reliability, or capacity.
- The expansion money is not by itself bad, and in fact should grow by $55 billion at the expense of SOGR, but I worry about cost control. I’m just not sure how to express it in Washington policy language, as opposed to agency-level language regarding in-house design, more flexible procurement, civil service independence, adoption of foreign best practice and not just domestic practices, keeping station footprints small, using cut-and-cover more, and so on.
You should go watch the whole thing, which has some on-screen links to the breakdowns above, but it’s a 1:45 video.
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.
A country or region that is good at manufacturing cars can export them globally and earn hard cash. But what about public transportation? How can a city that has the ability to build good, low-cost public transport get rich off of it? There is an answer, but it is more complicated than “export this,” mirroring the fact that public transport itself is a more complex system to run than cars. This in turn relates to housing growth rates and urban economies of scale, making this the most useful in a large city with high housing production rates, of which the best example is Seoul. The good news is that the world’s largest and richest cities could gain tremendously if they had better public transport as well as high housing growth rates.
Infrastructure is not exportable
I wrote more than two years ago about the difference between dirty and clean infrastructure. Cars, car parts, and oil are exportable, so the majority of the cost of cars as a system are exportable, making dedicated regions like Bavaria, Texas, and the Gulf states rich. Green tech is not like that – the bulk of the cost is local labor. A large majority of the operating costs of a subway system are local wages and benefits; in New York, depreciation on rolling stock is less than 10% of overall operating costs. Construction costs are likewise almost entirely local labor and management, which is why they are determined by where the project takes place, rather than by which engineering firm builds the project.
The upshot is that Madrid and other low-cost cities can’t just get rich by building other cities’ infrastructure for them. They can’t build turnkey systems for New York and London at Spanish prices – the problems with New York and London come from local standards, management, and regulations, and while a Spanish engineering firm could give valuable advice on what high-cost cities need to change, it’s not going to reap more than a fraction of the construction cost saving in consulting fees.
Good transit as an amenity
What a city can do with low-cost construction is build a large subway network like Madrid, and use that as infrastructure to help local economic production. This works as both a consumption amenity and a production amenity. As a consumption amenity, it enables people to commute without needing to own a car, which reduces living costs and lets employers get away with paying less in nominal terms; this is a bigger influence on local firms, because international ones tend to use cost of living adjustments that make profligate lifestyle assumptions and factor in car costs even in cities where car ownership is low, like Singapore or New York.
As a production amenity, public transit also enables work concentration in city centers. This is separate from the observation that it allows workers to commute more cheaply – if a large city produces in a concentrated center, then without rapid transit, workers can’t get in at all. About 23% of people entering the Manhattan core on a weekday do so by car per the Hub Bound Report, but at the peak hour, 8-9 am, this falls to 9%, because the road capacity is capped around 55,000 cars an hour and a maximum number of parking spots for them. Auto-centric cities of New York’s approximate size exist, not by building massive road capacity to support comparable city centers, but by not having strong city centers to begin with. Los Angeles has maybe 400,000 people in the widest definition of its central business district, where in the same area New York has more than 2 million – and Los Angeles’s secondary centers, like Century City, top in the mid-5 figures before they get completely choked with traffic.
So what a city can do with cheap infrastructure is build a large subway network and support a large high-rise central business district and then use that to produce more efficiently. This is possible, but more complex than just exporting cars or oil, because to export cars one just needs to be good at making cars, and to export oil one just needs to have oil underground, whereas to produce out of public transit one also needs a solid economy in other sectors that can make use of the better infrastructure. I suspect that this is why Southern Europe keeps not growing economically despite building high-quality public transport – the Madrid Metro is great but there isn’t enough of a private economy to make use of it.
The connection with development
To maximize the use of a subway for its economy, a city needs to make sure development can follow it. This means that city center needs high job density, which includes high-rise office towers at the busiest intersections, and many mid-rise office buildings in a radius of a few kilometers. Neither the typical European pattern in which there are few skyscrapers nor the American pattern in which there are skyscrapers for a few blocks and then the rest of the city is subject to strict residential zoning is ideal for this. It’s better to have a city whose central few square kilometers look like Midtown and whose surrounding few tens of square kilometers look like Paris, with the occasional secondary cluster of skyscrapers at high-demand nodes; let’s call this city “Tokyo.”
Residential development has to keep up as well. A city region that has a strong private economy but doesn’t build enough housing for it will end up with capped production. Normally it’s the lowest-end jobs that get exported. However, two problems make it more than a marginal reduction in production. First, expensive cities have political pressure to allocate apartments by non-market processes like rent control, keeping less productive but politically favored people; a large gap between market rent and construction costs creates plenty of surplus to extract, and a mass exodus of firms from cities like San Francisco in such a situation starts from thee least profitable ones, and by the time it affects the most profitable on, the system is entrenched. And second, breaking a firm’s chain between high-end headquarters jobs in a rich city center and lower-end subsidiary jobs elsewhere reduces firmwide productivity, since many connections have to be remote; Google has problems with all-remote teams and tries to center teams in the Bay Area when it gets too unwieldy.
For one example of a city that does everything right, look at Seoul. It has low construction costs, around $150 million per kilometer for urban subways. Thanks to its low costs and huge size, it keeps building up its system even though it already has one of the largest systems in the world, probably third in ridership after Tokyo and Osaka when one includes all commuter lines. It also has high density, high-rise CBDs, and fast housing construction; in 2019 the Seoul region built around 10 units per 1,000 people, representing a decline since the mid-2010s, and the state has plans to accelerate construction, especially in the city, to curb rising prices. This is till a better situation than the weak economy and flagging construction in much of Europe, or the NIMBY growth rates of both much of the rest of Europe and the richest American cities.
An online conference just concluded in which I gave a half-hour presentation about construction costs. Instead of giving my usual spiel, showing parts of our growing database and pointing out patterns, I spent a lot of time on why this is important. I’d written about this before, twice, but I’ve since looked more carefully at an example of two countries that are similar enough in their rail and public transit tradition that their large difference in costs must be the primary reason one has a bigger and more successful urban rail system than the other. I focused on developed countries, that is countries that manifestly have high incomes, good public health, good education, and so on; however, I believe the importance of costs is also a big reason behind delays in public transportation in high-cost developing countries like India.
You can read the slides here; this was recorded, and I’ll update this post with a link when it gets published.
Proof-of-payment with ungated train stations is a useful technique for reducing construction costs. It simplifies the construction of stations, since there is no need for a headhouse or mezzanine – people can go directly from the street to the platform. A station without fare control requires just a single elevator, or two if side platforms are desired, and can be built shallowly using cut-and-cover. Cities across the size spectrum, perhaps only stopping short of hypercities, should take heed and use this to build urban rail more cheaply.
Is this a common cost control technique?
No. The vast majority of low-construction cost countries use faregates, which is why I was reticent to recommend proof-of-payment as a cost mitigation strategy. Spain, Italy, Korea, and Sweden are all faregated; among the world’s lowest-cost countries, I believe only Finland and Switzerland use proof-of-payment fare collection on urban rail.
However, there are exceptions. In Italy, the Brescia Metro uses proof-of-payment. This is not typical for the country or the region – Italian metros have fare control, like the vast majority of systems outside Germany and Germany-influenced countries. However, because Brescia is small, the system was forced to engage in value engineering, removing scope that would be routine in larger cities like Milan. The majority was built cut-and-cover or above-ground; the typical urban Italian metro is entirely bored. Italian metro systems prefer short stations on new lines to minimize costs and provide capacity through automated operations and extremely high frequency; Brescia takes this to an extreme and has 30-meter trains. Among these cost minimization tactics is the lack of fare control. The result of this entire package is that Brescia spent 915 million euros on a 13.7 km metro system.
Station size and station cost
So far, we believe that the cost of the station, excavation excluded, should be proportional to the floor area. This is based on something told to us in an interview about electrical system costs for the Boston Green Line Extension, which is light rail in a trench rather than a tunneled metro system, so I recommend caution before people repeat this uncritically.
Moreover, on somewhat more evidence, it appears that the cost of station excavation should be proportional to the volume excavated. Some of the evidence for this is circumstantial: media reports and government reports on the construction of such urban rail projects as Second Avenue Subway, Grand Paris Express, and the RER specify the volume of excavation as a measure of the difficulty of construction. But it’s not just circumstantial. In Paris, the depth of some of the GPX stations has led to some construction complications. Moreover, preliminary interviews in Paris suggest, albeit not definitively, that station construction costs are predominantly a matter of dig volume. Finally, the insistence on short platforms and high frequency as a cost saving technique on new-build metro systems in Italy as well as in Denmark and on the Canada Line in Vancouver is suggestive too, even if it says nothing about whether the relationship between volume and cost is linear, degressive, or superlinear.
How does one minimize station costs with POP?
Proof-of-payment means that there is no fare control between the street and the station. This means any of the following ways of constructing station access become available:
- Cut-and-cover with the platform on level -1, with direct stair and elevator access from the street. The Berlin U-Bahn is built this way, with access points in street medians where available, such as U8 on Brunnenstrasse. It’s easy to build staircases at each end of the platform to increase access, with an elevator in the middle.
- Bored tunnel with large enough bores to fit the platform within the bore. The Barcelona method for this is to use 12-meter bores, but smaller, cheaper versions exist with smaller trains, for example in Milan. It’s also possible to use double-O-tube TBMs for this, but ordinarily they are more expensive than twin bores. Access involves vertical bores down to the platform with elevators or slant bores with escalators; there is no need for intermediate levels or entry halls.
- Bored tunnel with cut-and-cover stations, with no mezzanine levels. Here, the dig volume is unchanged, and the saving from lack of fare control is only in the finishes and elevator costs, not the excavation.
It is noteworthy that the most common technique for metro construction, by far, is the last one, where the savings from POP are the smallest. The vast majority of world metros have fare control, including in low-cost countries, and this perhaps makes metro builders not notice how two separate ways of reducing costs – cut-and-cover and POP – interact especially well together. Nonetheless, this is a real saving.
What does this mean?
A technique can be uncommon in low-cost countries and yet be useful in reducing construction costs. It is useful to think of the way Madrid, Milan, Turin, Stockholm, Oslo, Helsinki, and Seoul build their urban rail systems as good, but not always perfect. A trick that these cities might not pay attention to may still be good. The caveat is that it requires a good explanation for why they have not employed it; in the case of Italy, I believe it’s simply that the non-German world views fare control as the appropriate way to run a metro system and POP as a light rail technique and therefore only good for low-volume operations. There may also be backward compatibility issues – Brescia is a new build, like POP Copenhagen, whereas Milan is building extensions on top of a gated system.
Nonetheless, the evidence from station costs, the success of POP operations in Germany even on very busy lines, and the experience of Brescia all suggest that POP is good for metro construction in general. Cities smaller than New York building new systems should use it exclusively, and cities that already have faregates should tear them down to improve passenger circulation and facilitate the construction of POP lines in the future at lower cost.