This is a partial data dump from an in-progress database I’m compiling for subway construction costs around the world. The key point is that costs are rising: in cities with enough historical data points we can see a secular increase in construction costs. The difference between expensive cities like New York and London is that their costs have been high for a while, whereas cheap ones like Madrid and Seoul are seeing construction cost growth from a very low basis.
As a note of caution, while growth in costs seems universal, the rate of growth is not the same everywhere. Some cities, most notably Singapore and Toronto, have seen a cost explosion in the last 15-20 years; others, most notably Seoul, have seen only a moderate increase in costs.
I also urge readers to look at some 20th century historical costs here, as in this post I am going to focus on the very end of the 20th century and the 21st century.
Paris: the original Metro Line 14 cost €1.174 billion for 9.2 km (link), built between the 1990s and 2007; deflated to 2012 euros, the baseline year used for ongoing extensions, this is around €160 million per km. More recent projects in Paris cost around the same, including the Line 1 extension and Grand Paris Express – but those are mostly suburban extensions, whereas M14 had to go underneath central Paris.
Toronto: Jonathan English, who has been working with me on Canadian construction costs issues, notes that the Sheppard subway, opened in 2002, cost C$1 billion for 5.5 km, but ongoing projects are far more expensive. The one-stop 6.2 km Scarborough subway is projected to cost around C$3.5 billion not including extra items for interfacing with the existing rapid transit line along the same alignment, which is to be dismantled. Not only is the nominal cost 3 times higher – and the real cost is still around twice as high – but also the Scarborough subway has just one station to be constructed, which makes it a simpler project.
Montreal: Jonathan equally looks at the cost explosion in Montreal. The Laval extension was built in the 2000s and opened in 2007, costing C$742 million for 5.2 km and 3 stations, or C$143 million per km, crossing under the Rivière des Prairies. In contrast, an extension of the Blue Line planned for next decade is to cost C$3.9 billion for 5.8 km and 5 stations, or C$672 million per km – and even adjusting for inflation only reduces the cost differential to a factor of about 3.
(In case Canadian readers wonder why I’m not covering Vancouver, even though the escalations on the Broadway subway have pushed its per-km cost well beyond that of the Canada Line, the reason is that the Canada Line was built cut-and-cover whereas the Broadway subway will be bored.)
Singapore: Singapore’s cost overrun history in the 21st century has been unusually severe. Built mainly in the 2000s, the original Circle Line cost S$10 billion for 33.3 km, or S$300m/km, an overrun of 50% over the original budget. Subsequently, the Downtown MRT Line, built from 2008 to 2017, cost S$21 billion for 42 km, and the Thomson Line S$24 billion for 43 km. The Thomson Line has a complex interchange at Orchard, but also long segments in easy suburban areas – Upper Thomson Road, after which it is named, is very wide and borders modernist housing projects on one side and a forest on the other. Moreover, the last stage of the Circle Line, completing the circle, is to cost S$4.85 billion for 4 km and 3 stations – depending on PPP rates, it may be the first line outside New York to cross the US$1 billion/km line.
Seoul: South Korean costs are fairly stable. JRTR has data for the Seoul Metro going back to its start in the 1970s. After adjusting for inflation, costs were initially about $70 million per km, and rose gently to $80-90 million. The cost increases are continuing, albeit at a slow pace. As best as I can tell, the 2020s’ expansion program is budgeted at about $110 million per km in PPP terms.
Madrid: in the 1995-2003 period the city built tunnels for very low costs. The 1995-8 program cost $55 million per km, all underground, and the 1999-2003 program cost €3.147 billion for 74.7 km, 77% underground, around $52 million per km based on the era’s PPP conversion rate. In the conditions of 2010 this would be roughly $65-70 million per km – but the Line 2 extension, built 2008-11, cost €315 million for 4.6 km and 4 stations, and the Line 9 extension, built 2009-15, cost €191 million for 3 km and 2 stations, about $80-90 million per km.
Update: since people have asked for high-speed rail data, it confirms the same story. Ferropedia has costs in Spain, which have risen from €4.88 million per kilometer in 2001 terms for Madrid-Seville, which opened in 1992, to about €15-20 million per kilometer in 2006-7 terms for subsequent lines from the 2000s and 2010s. France displays the same history of escalation: built in the early 1980s, the LGV Sud-Est cost €5.5 million per km, much less than the late 1980s and early 1990s’ LGVs Nord and Atlantique (which cost €10 million), let alone this decade’s LGV Est (which cost €16 million for Phase 1 and €19 million for Phase 2); all of these lines are through comparable terrain, with very little to no tunneling.