I’m about to send a thinktank a draft of a table of subway construction costs, and I’d like to preview one of the most important findings from the data. This is based on 125 distinct items, totaling 2,297 kilometers – some complete, some under construction, a handful proposed. I’ve alluded to this here before, for example when writing about national traditions (US, Soviet, UK) or about Russian and Nordic costs. But the basic observation is that construction costs are not really a feature of an individual metro line, but of a city, and usually an entire country.

What this means is that if one line in Madrid is cheap, then we can expect other lines in Madrid to be cheap, as well as in the rest of Spain; if one line in London is expensive, then we can expect other lines in London to be expensive, as well as in the rest of the UK. In fact, in both countries the construction costs of metro systems in the capitals also accord with the construction costs of intercity high-speed rail: cheap in Spain, expensive in Britain, with Germany somewhere between Spain and Britain and France somewhere between Spain and Germany.

Some examples

The examples in this section are somewhat cherrypicked to be the ones with narrower ranges, but there are very few examples with truly large ranges over a similar period of time (i.e. not secular increases as in Canada). I am specifically excluding regional rail, as it tends to be more expensive per kilometer than subways.

Panama: Line 1 cost around PPP$260 million per kilometer for 53% underground construction, and Line 2 is cheaper, around $150 million, but is entirely above-ground. This is consistent with a factor-of-2.5 underground premium over elevated lines, well in line with the literature.

Greece: Athens Line 4 is €104 million per km, with construction having started recently. Thessaloniki has two lines in the database, the main line due to open next year and an extension to Kalamata due to open in 2021, and Athens is also about to wrap up an extension of Line 3 to Piraeus. All cost figures may be found here on PDF-p. 9. The two Thessaloniki projects are respectively €135 million/km and €118 million/km, the former at least including rolling stock and I believe the latter too; the Athens Line 3 extension, without rolling stock and with somewhat wider stop spacing, is much cheaper, €61 million/km, but this rises to €82 million/km with rolling stock.

Sweden: the Stockholm Metro extensions under construction all cost pretty much the same per kilometer. Three extensions are under construction at once, in three different directions; per this source, the costs per kilometer (in kronor) are 1 billion, 1.25 billion, and 1.15 billion, with the most expensive of the three involving brief underwater tunneling.

Russia: I asserted in an old post that Russian construction is expensive, with only a handful of projects. Since then I’ve found a source asserting that the entire 2011-20 program is 1.3 trillion rubles, for what appears to be 150 km, 57% underground. This is in PPP terms $364 million per km. Other costs are vaguely in that range – Railway Gazette claims the cost of boring in Moscow is (again in PPP terms) $400-600 million/km, Line 11 is around $310 million/km for underground suburban construction, one line mentioned on Railway Gazette in St. Petersburg is $310 million/km underground, another St. Petersburg line is maybe $360 million/km.

What does this mean?

That there’s correlation between different cities’ construction costs within the same country suggests the differences in costs are predominantly institutional or socio-political, rather than geological. This is further reinforced by looking at countries with very similar socio-political regimes, namely the Nordic countries: all of them are cheap, and even though Stockholm and Helsinki both have similar gneiss geology, the Oslo line I use for comparison does not (and neither does somewhat more expensive Copenhagen).

To further reinforce the institutional point, the costs of high-speed rail in different countries seem to follow the same order as the costs of metros. Spain is cheap: Ferropedia quotes construction costs below €20 million per kilometer. The UK, in contrast, just announced a cost overrun on HS2, a 540 kilometer network, to £88 billion, and even allowing for future inflation, this is maybe 7 or 8 times as expensive as in Spain. France and Germany are in between, in the same order as their metro costs. China, as far as I can tell comparable to France in its metro construction costs, has a high-speed rail construction cost range somewhat higher than France’s, mostly explainable by using more (generally avoidable) viaducts.