Tokyo Construction Costs
Here is a list of Japanese subways and their construction costs, courtesy of Borners, who has been working on this as well as on a deep dive about London construction costs. I’d been looking for this data for years; someone in comments posted a link to a different sheet summarizing the same data years ago but I couldn’t find it.
Unfortunately, the list isn’t quite good enough to be used for all subway lines. The problem is that the numbers are given in nominal yen for the costs of constructing entire lines, including ones that opened in phases over many years during which inflation was significant. The table of lines and their construction costs in units of 100 million yen/km is as follows, with my best attempt at deflating to 2023 prices, still in units of 100 million yen/km; to convert to millions of dollars per km, the 2022 PPP rate is $1 = ¥94.93, so add 5.3% to all numbers in the penultimate column.
| Line | Cost/km | First works | First opening | Final opening | Year of prices | Cost/km (real) | Confidence |
| Marunouchi | 18 | 1951 | 1954 | 1962 | 1956 | 114 | Medium |
| Asakusa | 46 | 1956 | 1960 | 1968 | 1961 | 257 | Medium |
| Hibiya | 32 | 1959 | 1961 | 1964 | 1961 | 179 | High |
| Tozai | 41 | 1962 | 1964 | 1969 | 1965 | 181 | High |
| Mita | 91 | 1965 | 1968 | 2000 | 1975 | 182 | Low |
| Chiyoda | 69 | 1966 | 1969 | 1979 | 1970 | 236 | Low |
| Yurakucho | 167 | 1970 | 1974 | 1988 | 1979 | 261 | Low |
| Hanzomon | 255 | 1972 | 1978 | 2003 | 1983 | 336 | Low |
| Shinjuku | 235 | 1971 | 1978 | 1989 | 1976 | 433 | Low |
| Namboku | 262 | 1986 | 1991 | 2001 | 1993 | 291 | High |
| Oedo | 311 | 1986 | 1991 | 2000 | 1994 | 343 | High |
| Fukutoshin | 282 | 2001 | 2008 | 2008 | 2005 | 314 | High |
The confidence level is a combination of the length of time it took to build the line and the inflation rate over that period. The Oedo and Namboku Lines opened in stages over a decade, but during that decade Japan had no inflation, and as a result price level adjustments are easy. In contrast, inflation in the 1960s was high but the Hibiya and Tozai Lines were built quickly, so that the uncertainty based on picking a year to deflate to is maybe 10%. The in between lines – Mita, Chiyoda, Yurakucho, Hanzomon – all opened in stages over a long period of time with significant inflation. This makes it hard to use them to answer the question, what was Tokyo’s cost history?
What the numbers suggest is that by the 1970s, construction costs were not much lower than they’d be in the 2000s; Japan having grown steadily in the 1970s and 80s, this means that its ability to afford new subways after the bubble burst in the 1990s was actually greater than in the 1970s. Construction costs have risen since – an extension of the Namboku Line to Shinagawa is budgeted at ¥131 billion/2.5 km and a branch extension of the Yurakucho Line from Toyosu to Sumiyoshi is budgeted at ¥269 billion/4.8 km. Toyosu-Sumiyoshi is in Shitamachi and has multiple canal crossings justifying an elevated cost, but Shirokane-Takanawa-Shinagawa is in easier topography, and while it has multiple subway crossings over a short length, so did the lines built in the 1990s and 2000s – the Fukutoshin Line has, over 9 km, five subway crossings and complex connections at both ends with through-running.
Pedestrian Observations 
Yes any extra data is welcome!
Just to add some extra context to what Alon says above, I’ve managed to get pretty much every city in Japan’s construction costs for metro projects pre-2000 except for Tokyo, Osaka and Kyoto. The document linked by Alon shows that a dataset is clearly in the hands of policymakers and the writers of the above Japan Subway Association document.
Some cities have published that data in other areas.
E.g. Sapporo’s official website
https://www.city.sapporo.jp/st/subway/gaiyo/gaiyo.html
And Nagoya has put pretty much every section in its official history
Nagoya has published it all online (warning pdf mania)
https://www.kotsu.city.nagoya.jp/jp/sp/ENJOY/TRP0004710.htm
And thank god for that since the Meiji-Meiko line system in Nagoya maybe have the most divided set of sections of any Japanese metro line, the official cost table breaks it down into 8 sections built between 1965 and 2004.
As for whether construction costs have increased, I think there is good evidence for it at the moment. And we have clear evidence for increasing costs in HSR lines too (I have updated the public TCP database with the remaining post-1987 lines*, the older ones are coming once I get round to them).
I don’t yet see a clear organisation change since the builders are still JRTT, or Tokyo’s Infrastructure department. There some special delivery vehicles for some, but that not especially new, and previous consortium units worked fine.
Two factors that are particular to Japan. One there is clearly a worker access crisis in Japanese railway industry at the moment as the Boomers age out of both the operations and construction workforces**. That shortage in context of stagnant wages economy wide has led to “Workplace reforms” i.e. guaranteeing two day weekends and waaay less overtime.
Second factor maybe something to do with land costs, Japan has weak eminent domain, and land prices in the major cities have recovered from the their ca.2000 lows furthermore infill development in these locations has made it more difficult as there are more buildings/residents to buy out and more complex basement/piles etc too.
And in my studies on infill stations on existing above ground lines, Tokyo is often much more expensive than other locations for comparable infrastructure e.g. Keiyo line’s Makuhari-Toyosuna cost 126億 yenn, while JR West’s Sojiji station cost 60億, JR Tokaido’s Mikuriya 49億 and JR Kyushu’s Kaizuka station is 13億. That difference pretty well lines up to local land costs.
Plus Alon undersells the difficulty of the Namboku extension to Shinagawa which can’t follow a public street and has to avoid not just the Asakusa line but also Keikyu’s connecting tunnel and new underground platforms, plus set up for extensions south of Shinagawa in the future which includes the Chuo shinkansen.
*Akita/Yamagata mini-shinkansen are different ballgame I haven’t included them.
** The Rail industry has only just started to hire foriegners, but the kind of skilled blue-collar work has not been the focus of immigration policy until the last 5 years. MLIT is working on it. But certainly nothing like the Anglophone European construction labour market Alon chronicles in the Stockholm case study.
Weren’t Oedo and Fukutoshin deep-bored, so the presence of a street wouldn’t matter?
Not in the Japanese easements regime, Japanese subways follow street alignments as much as possible for a reason. Follow Oedo and Fukotoshin and you can how both try to do so as much as possible. Its also why in a bunch of places you have lines on top of each other for the most expensive areas of land (e.g. Ginza-Hanozomon, Mita-Chiyoda, and in Osaka Hanshin-Kintetsu Namba line-Sennichimae). I think its one of the reasons why Osaka was so insistent on the grid pattern even though its clearly underperformed Tokyo in the end.
Not sure about Japan but certainly in Britain domestic construction costs have risen too. My house cost £60k to buy in todays money when it was first built in 1960, now it has been extended since but the rebuild cost now on the insurance is £300k.
Presumably the original construction costs were at most £40k adjusted for inflation and for now assuming some degree of caution from the insurer maybe like £240k today, if we assume that half the current cost is the extension/quality increase in modern construction you are looking at maybe an increase of 3x over that time for the same thing.
Its not quite a clean comparison. Housing and repair is just more labour intensive relative to other manufactures, even in places with high use of prefab (UK is low in its use). Tunneling has had labour saving tech thanks to TBMs and NATM etc which why costs haven’t skyrocketed in just high-wage countries.
Right and it would be even more labour intensive than a new build as it has to fit with the house it is attached to as it is semi detached and you would obviously be constrained by the surrounding homes too.
Very much an upper bound then!
Looks like the Toei lines (Asakusa, Mita, Shinjuku, Oedo built by the city government) are pretty consistently more expensive than the Tokyo Metro lines (built by the national government, except for the Ginza line I think?). There are exceptions: the Mita line is relatively cheap, and the Hanzomon and Fukutoshin lines are expensive. The cost of the Fukutoshin line (a deep bore line going through some pricey territory) seems like it should be high, but I’m not sure about the other outliers.
Yeah, Ginza was originally 2 distinct private metro projects using cut-and-cover primarily (hence the alignment).
I think any Toei/Tokyo difference from above is primary an artifact of how recent the line is and where it goes. I’m a bit suspicious of why Shinjuku was so expensive given its timing, and its not tunnelling in areas that much worse than the Tozai line.
Could be the weird gauge or the express service?
Scotch guage is between Narrow and Standard (closer to the latter) so its not really different in terms of building. The cost would be in the rolling stock if at all. Yeah Shinjuku does use more passing loops than others.
I’ve found some evidence its about takings.
Click to access 15(1)-2-0883.pdf
Also the bit where it doesn’t follow streets is the newer bit that was built later than the other sections.
Indeed, there are mentions (in the Japanese Wikipedia entry) of tunneling through soft soil and under buildings, requiring underpinning and/or replacement with more stable fill. Furthermore, the nature of the line as a cross-city route resulted in many junctions. The route under Shinjuku Station (or rather the then JNR Shinjuku freight station just south) required especially deep tunneling to clear the planned but never realized three story underground Joetsu Shinkansen platforms. This tunneling work was subcontracted out to JNR construction.
Soil is a problem for any line going through the Shitamachi/sumida where its either alluvial or reclaimed land plus urbanised as hell. ~shudder~
Tozai and Keiyo lines were lucky to have sections of reclaimed land/salt flats that it could just EL over (Kasai), Shinjuku couldn’t do that.