Michael Todd has a disappointing article in Miller McCune arguing that High Speed Rail projects are likely to go over budget. His justification is, well, that they're large capital projects, and large capital projects often go over budget. Yes, they do. But this isn't an argument against high speed rail or any other major capital project. It's an argument for better approaches to cost estimation and control.
Nowhere does Todd justify the implication that high speed rail projects are at greater risk of cost overrun than, say, huge urban freeway tunnels such as Boston's Big Dig, Sydney's Cross-City Tunnel, or the likely tunnel in downtown Seattle's future.
But I'm grateful to Todd for linking to a very useful 2008 article by Ryan Blitstein on the work of Danish economist Bent Flyvbjerg. Read it. It's a good overview of Flyvbjerg's important work on cost overruns and strategies for predicting them. For more, see Flyvbjerg's book Megaprojects and Risk.
Note, by the way, that the problem of cost overruns is conceptually separate from questions about why capital costs, predicted or not, are so high.