True, but if we built any other sort of infrastructure (water, sewage, electicity) that operated at above over 100% capacity from day one, wouldn't we consider

True, but if we built any other sort of infrastructure (water, sewage, electicity) that operated at above over 100% capacity from day one, wouldn't we consider a solution with more capacity? With the light rail already blowing out as of November last year from $1.6bn to $2.1bn [1] I can't help but think of the merit of heavy rail. My understanding is heavy rail is very expensive, but how much more? I haven't been able to find a comparison of a heavy rail design on this route. [1]: http://www.theaustralian.com.au/news/nation/sydney-cbd-and-eastern-suburbs-light-rail-project-500m-cost-blowout/news-story/29ffab19ad08da08fb7bcde90bdaeaa8 http://www.theaustralian.com.au/news/nation/sydney-cbd-and-e...