An article from last week about a cost saving push in Seattle made me think again about how learning from lower-cost examples works. As the costs of the majority-above-ground Ballard extension are careening toward the $2 billion/km mark, the agency and civil society are looking for cost savings. Scott Kubly, the former head of the Seattle Department of Transportation, is proposing to reduce the costs of stations by shortening the platforms, citing Copenhagen’s combination of driverless operations and very short trains as a cost saver. Kubly says,

They built it at about a quarter cost. How they did that was shorter, more frequent trains, which leads to smaller stations, which leads to less excavation, which leads to faster delivery and a better passenger experience.

This, to be clear, is at best a second-order saving. The issue is that Copenhagen’s short trains and driverless operations are more or less unique to it, but its medium-low costs aren’t. An honest program of learning from Scandinavia ought to learn from all of the Nordic capitals at once, as much as possible, and focusing on what’s common to them and not on the differences. Stockholm in particular has lower construction costs than Copenhagen these days and has longer trains than Seattle: Stockholm T-bana trains are 140 m long (and Citybanan, with 200 m trains, cost $400 million/km in 2025 prices, less than a quarter as much as Ballard), Link trains are designed up to 116, Copenhagen Metro trains only 39. Nya Tunnelbanan manages lower construction costs than Copenhagen these days, so learning from low-ish Nordic costs should not center the combination of driverless trains and short platforms.

More broadly, this proposal by Kubly (and by the generally good Robert Cruickshank, formerly of California HSR Blog) is convincing me that the real strength of the Transit Costs Project is that we’ve done deep dives into more than one success case. We technically have three low-cost cases: Stockholm, Istanbul, and a selection of Italian cities. But in Stockholm, too, the case looked at trends common to the Nordic countries, namely, the unfortunate tendency in all four to privatize project planning to international design-build consortia. Our conclusion also uses some medium-cost Parisian examples to check itself as well as a few German and Spanish specifics, and we’ve increasingly looked at some Chinese examples, though well short of a full case like our main three. We’re blinder than we’d like to be in East Asia, especially low-cost Korea, but our coverage in Europe is fairly good and we have at least some idea of what’s going on in Latin America. Our ideology is always that it’s most important to look at the commonalities of the places that work when distilling the best practices, rather than on the differences.

This matters, because the average Continental European (or Chinese) just doesn’t think about the United States when doing transportation engineering. A Swede, asked about the features of their transportation program, will focus not on what makes the difference between Scandinavia and the United States, but on the differences between Sweden and the other Nordic countries. The literature I saw when I wrote the Sweden case was replete with intra-Nordic comparisons, on every conceivable measure. Most of the literature came from the country I was researching, but some came from the other three Nordic countries. All of them are like this. Ask a Swedish planner about what makes Nya Tunnelbana work and they’ll cite pertinent features like the drill-and-blast construction method and why it’s superior to tunnel-boring machines, where Copenhagen in fact uses TBMs just fine; ask a Danish one and they’ll talk about the driverless operations and extremely high frequencies.

And this generalizes. Italy has used very short stations and driverless operations to keep down the costs in very small cities like Brescia, and somewhat longer but still short stations in Milan, but Rome Metro Line B1 uses 110 m long trains and was built for $300 million/km in 2025 prices. While Italians talk about this as a cost saver, Manuel Melis Maynar wrote positively of Madrid’s rejection of driverless operations as an example of cost saving through technological conservatism. I don’t doubt that in both cases they were right under the circumstances (Melis having written of extensions built 25 years ago), but just as the medium-low costs of the Nordic countries have to be properly attributed to shared features, the even lower costs in Southern Europe have to be properly attributed.

Far more important than looking at a Copenhagen-specific feature is answering all of the following questions, in increasing order of abstraction:

• How large are the underground stations compared with the train length? How standardized are their designs?
• How standardized are the RFPs for station finishes, signals, and electrical and mechanical systems?
• Is there a single point of homologation for the system, or can a single suburban fire department demand construction in excess of code because the fire department head objects (as happened in Bellevue across Lake Washington)?
• Does contracting follow good practices (i.e. the traditional system as used in Scandinavia until about 15 years ago), or is everything done with layers of consultants managing other consultants with opaque design-build contracts? Are contracts itemized or fixed-price? Is there technical scoring to ensure contractors race to the top and not the bottom?
• How large is the in-house planning and supervision team? Does it have the capacity to manage a project the size of ST3, or even a single subway line like the combination of Ballard and West Seattle?
• Are priorities decided by professionals or by political appointees? Does funding follow the Acquis or possibly another similar system governed by rule of law? Is a cost-benefit analysis mandatory, and do project designers expect that a poor cost-benefit analysis will lead to project cancellation?

Each of these questions, by itself, represents a cost saving larger than anything that could come from shrinking the stations based on driverless operations, a tradeoff that reduces station dig costs but increases systems costs and works in many places but is never going to turn American costs into Southern European or Nordic costs. In contrast, relying on one simple trick like Copenhagen’s requires deep understanding of why each of Copenhagen and Stockholm does what it does, which understanding is unlikely to exist in anyone who doesn’t know that these cities have comparable costs, both a fraction of the United States’.