I sincerely hope that these sleepers turn out to be a howling success.Agree YM, was wondering about the weight of the sleepers, as well...for the stability as you've said, but casting the mind back a while, wasn't there some experimental work going on with treated pine sleepers, which also wound not be very heavy.
So far, I have been unable to find any real details as to their cost, weight, axleloads, dimensions and/or number per km etc. I am struggling, however, to see that they will have the weight to contribute to track stability to more or less the extent of concrete.
As I have said, I hope that that they do work to save the trees and support a decentralised industry, if for no other reasons.
I think from some discussion about them, someone said the sleeper weight had bugger all to do with the stability, which was the reason I thought Red Gum or certainly Hard Wood, was used, because it's bloody heavy.
In interpreting the info in the link provided by Alphatron, it seems that they go about 30 to the tonne (no mention of section or length), compared to hardwood (std gauge) of about 12/tonne, steel 20/tonne and concrete 4/tonne. It seems a lot of their field testing has been in QLD, maybe that 30/tonne is for 1067 gauge sleepers.
They are probably very good for applications such as secondary lines, sidings, heritage lines, & etc. I think it will be a while before they challenge concretes in the 22 - 25TAL range at 100 - 160km/h.
What I'm really interested in is seeing how they go in replacing timber transoms