Earlier quoted context omitted.
According to the Sydney Morning Herald, one-third of buses will still be required when the light rail starts operating in 2019 due to insufficient capacity, rising to 80% of current buses by 2031! http://www.smh.com.au/nsw/sydney-cbd-and-south-east-light-ra...
I never really thought that light rail would replace buses completely. One can't help but imagine how many more buses we would need without light rail, no?
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-e...