Auckland Council and the Government have recently signed an official agreement to jointly fund the City Rail Link (CRL) – a move that both had previously committed to in principle, but not on paper. This is good news for the city, as it gives us certainty about how CRL will progress. (It is also a fine example of the value of good analysis and patient persuasion – this government was initially very skeptical of the project but has gradually changed its tune.)
Given Auckland’s constrained geography and lack of future transport corridors, CRL probably won’t be the last major tunnelling project we investigate. If we want additional transport corridors, we’re going to have to reclaim land, build bridges, or dig tunnels.
So it’s worth asking: Are tunnelling costs reasonable in Auckland? Could they be reduced? These are important questions. The cheaper tunnelling is, the more transport corridors we’ll be able to buy in the future.
To help answer this question, Alon Levy at Pedestrian Observations compiled a nice dataset of construction costs for rail tunnels (part 1, part 2). He gathered data for over 40 rail tunnel projects that have been completed or planned over the last decade or so. While the data is a bit imprecise – based on a mix of ex-ante cost estimates and ex-post contract costs, and converted between currencies using purchasing power parity exchange rates – it provides a useful basis for benchmarking CRL costs.
According to the full business case released in July 2016, the midpoint estimate for the cost to construct and commission the CRL is $2.5 billion, once adjusted up for expected future inflation. Here’s how the cost profile is expected to go:
Converting this back to 2010 US dollars is not an exact science, because we’ve got to adjust for recent and future inflation and purchasing power parities between NZ and the US, but as a rough estimate I would say that the CRL cost is equivalent to around $1.4bn in 2010 US dollars. As CRL is 3.4km long, this equates to costs of around US$410 million per km.
Here’s a chart showing how CRL costs compare to the costs for 42 other urban rail projects. (Note that a number of the projects on the lower-cost end of the scale had significant above-ground portions that tend to be cheaper to build.)
All in all, the CRL is ranked 11th on cost – it’s on par with the costs of the Amsterdam North-South Line or Budapest Metro Line 4. It’s nowhere near as expensive as recent underground rail projects in New York or London, which tend to cost more than $1 billion per kilometre. But nor is it as cheap as metro extensions in Spain or South Korea, which cost more like $100 million per kilometre.
For reference, here’s a subset of the data for 19 projects, including the City Rail Link. This shows a few important facts:
- First, project costs vary more between countries than within countries – all of the projects in the US are ludicrously expensive, all of the projects in Japan are mid-pack, and all of the projects in Spain, Italy, and South Korea are cheap.
- Second, there is basically no correlation between project scale and per-kilometre costs. It isn’t necessarily cheaper (or more expensive) per kilometre to build longer tunnels. However, there are likely to be other economies and diseconomies of scale that are harder to observe, such as crowding-out when trying to complete too many projects at the same time.
|Rank||Project||City||Tunnel length||Approximate cost per kilometre (million 2010 USD)|
|1||East Side Access||New York (US)||2km||$4,000|
|2||Second Avenue Subway Phase 1||New York (US)||3km||$1,700|
|7||Central Subway||San Francisco (US)||2.7km||$500|
|8||Singapore Downtown MRT Line||Singapore (SG)||42km||$490|
|10||Amsterdam North-South Line||Amsterdam (NL)||9.5km||$410|
|11||City Rail Link||Auckland (NZ)||3.4km||$410|
|12||Budapest Metro Line 4||Budapest (HU)||7.4km||$360|
|13||Toei Oedo Line||Tokyo (JP)||40.7km||$350|
|14||Nanakuma Line Extension||Fukuoka (JP)||1.4km||$320|
|20||Paris Metro Line 14||Paris (FR)||9km||$230|
|26||Copenhagen Circle Line||Copenhagen (DK)||15.5km||$170|
|27||Barcelona L9/10||Barcelona (ES)||47.8km||$170|
|33||Naples Metro Line 6||Naples (IT)||5km||$130|
|34||Milan Metro Line 5||Milan (IT)||5.6km||$110|
|39||Seoul Sin-Bundang Line||Seoul (KR)||18km||$90|
|41||Helsinki Westmetro||Helsinki (FI)||13.5km||$70|
|42||Seoul Subway Line 9||Seoul (KR)||27km||$40|
|43||Barcelona Sants-La Sagrera Tunnel||Barcelona (ES)||5.8km||$40|
Lastly, we should be asking: What can we do to be more like South Korea or Spain when it comes to tunnelling costs? Some of the differences between locations are likely to be impossible to change, as they depend upon geography. But others are possible to change, as they relate to construction methods, design standards, and processes.
A few years ago, Alan Davies (Crikey) identified a few of these factors:
Toronto transit advocate Steve Munro… analysed a report by transit agency Metrolinx comparing the cost of tunnelling for Toronto’s new 6.4 km Sheppard Subway with that for the new 40.5 km MetroSur line in Madrid. Madrid is a popular benchmark because it has literally built hundreds of kilometres of new heavy/light rail lines over the last 40 years.
After adjusting for differences in how land acquisition is costed, he says the respective costs of Sheppard and MetroSur were $142.5 million per km and $87.1 million per km. Both lines opened at the same time. The key differences Mr Munro identifies are:
- No environmental assessment was conducted on MetroSur
- The standards for fire safety are more stringent on Sheppard
- Stations are 50% longer on Sheppard
- Non-tunnel construction was undertaken 5×12 on Sheppard, compared to 7×24 on MetroSur
- Sheppard was built with dual tunnels, MetroSur with a single tunnel. Mr Munro says “the trains in Madrid are smaller and require a smaller combined tunnel than would be the case in Toronto. Single tunnels eliminate the need for cut-and-cover box structures at crossovers and effectively reduce the scope of excavation at stations where these crossovers are located”.
- The use of cut-and-cover tunnelling on Sheppard was confined to stations, but it was used for 30% of MetroSur
- It was more expensive to tunnel through the glacial rocks and streams of Toronto than the compacted sand of Madrid
- MetroSur provided greater economies of scale as it was one of a number of projects. “Construction activities simply moved from one project to another rather than being reconstituted for each expansion, and more of the design was done during construction.”
- Sheppard has two large interchange stations over its 6.4 km, whereas MetroSur has five interchanges over its 40.5 km
Physical factors like geology explain a lot of the difference between Sheppard and MetroSur, but so too do standards. Community expectations on a range of variables – for example environmental standards, engineering and operating standards, safety standards, the level of citizen input – appear to be key drivers of higher costs in Toronto. It seems there is a very strong commitment in Madrid ‘to get on and get it done’.
In other words, if we’re going to build more tunnels in the future, we had best be prepared to commit to the concept and take a hard look at how we can get things done more cheaply.
What do you make of the data on tunnelling costs?