Relative Costs of Transit Construction
The relative costs of different technologies of transit are not fixed. Although there are some rules of thumb for the ratio of tunneling cost to above-ground transit cost, the actual ratio depends on the city and project, and this would favor the mode that’s relatively cheaper. Likewise, the ratio of operating to capital costs is not always fixed, and of course long-term real interest rates vary between countries, and this could again favor some modes: more expensive construction and cheaper operations favor buses, the opposite situations favor rail.
In general, els cost 2-2.5 times as much as at-grade light rail, subways 4-6 times as much, according to Table 6 in this Flyvbjerg paper; Table 5, sourced to a different previous paper, estimates per-km costs, and has ratios of 1.8 and 4.5 respectively.
However, specifically in Vancouver, the premiums of elevated and underground construction appear much lower. The cost estimates for rail transit to UBC are $2.9 billion for an almost entirely underground extension of SkyTrain and $1.1 billion for at-grade light rail along Broadway, both about 12 km. Elevated construction is in the middle, though closer to the light rail end: the estimates for the two all-elevated SkyTrain extension alternatives into Surrey are $900 million for 6 km for rapid transit alternative 3 and $1.95 billion for 15.5 km for alternative 1. The under-construction Evergreen Line, which is 11 km long of which about 2 are in tunnel, is $1.4 billion.
In the rest of Canada, this seems to be true as well, though the evidence is more equivocal since the projects that are considered above-ground are often elevated rather than at-grade. The Canadian above-ground projects that Rob Ford’s Eglinton subway is compared with are not wholly above ground. Calgary’s West LRT, which with the latest cost overrun is $1.4 billion (a multiple of the preexisting three-line system) for 8 km, includes a 1.5 km tunnel, a short trench, and some elevated segments. Edmonton’s North LRT is $750 million for 3.3 km, of which about 1 km is in tunnel and the rest at-grade. But while it’s hard to find the exact ratio because of those mixed projects, the costs are not consistent with the ratios found in Flyvbjerg’s sources.
Outside Canada, those ratios seem to hold up better. American above-ground transit projects, such as the Portland Milwaukie extension and the Washington Silver Line, are as expensive as Calgary and Edmonton’s light rail, but American subways are much more expensive than Toronto’s Eglinton subway ($325 million/km, 77% underground and the rest elevated): Manhattan tunneling is more difficult, so its $1.3-1.7 billion/km cost may not be representative, but conversely, BART to San Jose’s $4 billion for about 8 km of tunnel is for tunneling partially under a wide railroad right-of-way, with no crossings of older subway infrastructure as is the case for Eglinton at Yonge.
Conversely, French tunneling costs are comparable to or lower than Canadian ones, but at-grade light rail is far less expensive than in North America. The RER E extension was at least as of 2009 budgeted at €1.58-2.18 billion for 8 km of tunnel (see PDF-page 79 here; this excludes €620 million in improvements to the existing commuter lines the tunnel will be linked with) – somewhere between the per-km costs of Vancouver and Toronto subways, but in a much denser environment with more infrastructure to cross. But the cost range for Parisian trams is much lower, about €30-50 million per km, in line with the subway:tram cost ratio of 4-6; the cost range in other French cities tends to be a little lower.
What this means is that in Canada in general, and in Vancouver in particular, questions about what mode to build should have higher-end answers than elsewhere. It doesn’t mean that the Eglinton subway is justified, but it does bias suburban rail lines in Vancouver toward elevated SkyTrain extensions rather than light rail, and inner extensions toward SkyTrain subways. For the same cost of building a subway under Broadway, Translink couldn’t build too much additional light rail; it could build two lines, say on Broadway and 41st, or maybe three if both non-Broadway routes are short, but certainly nothing like the entire network that SkyTrain opponents believe is the alternative, citing European tramway construction costs.
Pedestrian Observations 
The rule-of-thumb given to me by someone I’ve been in contact with at AECOM’s LA office: elevated is 4x the cost of at-grade, and subways are twice the cost of that (i.e., 8x at-grade).
Also: where are you getting your BART-to-San-Jose data from? You should add that – and the French and Canadian numbers – to your original US rail construction costs post (which you claimed would be updated when you found new examples!). It’d just be nice to have as much data in one place as possible.
The cost number is the difference between the projected costs to Berryessa and Santa Clara in 2009 (link), sourced to an article that’s no longer online. I just measured the tunneled distance on Google Maps.
Eventually I’m going to just revamp the construction cost post, with forward links to third-world posts, more numbers, alternative links in case the links die, etc.
Hang on about the Eglinton line in Toronto: it’s actually a light-rail project with a significant on-street segment. Another section is actually involving the reconstruction of an existing automated light metro route. It’s definitely not directly comparable to a subway project. If you look at the Spadina-York subway extension, you’ll find a considerably higher per kilometre cost. The distinction isn’t Canada vs US, it’s Vancouver vs most of the rest of North America. Montreal also has some pretty impressively low per km subway construction costs.
To my shame, I’m using project descriptions from Wikipedia, but the Wiki is telling me 19.5 km out of 25.2 are underground. So yeah, it’s a subway. Are the stations unusually short, as on the Canada Line and the San Francisco Central Subway?
The Spadina extension is, according to the same source, $300 million per km. The northern end of the line is in “Why the hell is this even underground?” territory, but it doesn’t follow a consistent road, making it a bit harder than, say, tunneling under Santa Clara Street and two rail ROWs.
I assumed the costs and other statements about “Rob Ford’s Eglinton subway” in the original post were based on the pre-rebellion plans. Are they correct with that interpretation?
The Wikipedia article doesn’t seem to have been updated recently, so that was the old plan as proposed by Mayor Ford. A rebellion among the councillors on the transit commission restored the original plan, which includes about 6 kilometres of street median running in the middle of the line.
You’re absolutely right about the northern section of the Spadina extension. I’ve seen one of the many studies that preceded construction of the line, and it actually included a (brief) examination of an elevated section. Unfortunately, and entirely without considering the potential cost savings, it dismissed the possibility due to the potential for a mild inconvenience in terminal operations. It also refused to even consider the possibility of an elevated station at Vaughan Centre.
Did the rebellion reduce the cost at all, or is it still $8.2 billion?
That’s a very good question. They’ve been rather sketchy on the most recent cost estimates, but the most commonly quoted figure is around $6 billion. It’s not surprising that the Wikipedia article is out of date, since even the official website includes documentation from various iterations of the project.
A couple of things, the Evergreen line is not actually under construction yet, just relocating services etc and the bids have not been made public so costs are not fully known. The other is at grade costs on Broadway are likely to be significantly higher than average because of all of services that would need to be relocated and the fact that for all practical purposes Broadway would need to be rebuilt from sidewalk to side walk to accomodate at grade rail…..I am not sure why some of the Surrey at grade estimates are so high…
Also my understanding is things are still a little up in the air about the Eglington line others may have more info.
I’ve been trying to source costs per km/ station costs/ platform costs (Lrt/busway) etc. and Flyvberg has most detailed breakdowns including elevated options. 1983 $ are not 2013 $ however and I will update my cost analysis to 150% of Flyvberg’s 1983 numbers. You can see what I have so far, by checking dropbox link on my webpage http://www.johnrossharvey.com
Flyvberg’s info will change this, and I’d like to add elevated train option over our highway corridors to see where that sits relative to other Metrolinx budget numbers, which are far higher than any sources I can find.