115km/hr! 100 would be more than enough and 115 is for SG, we are talking NG in Tassie, Qld is 100km/hr max on straight track with concrete sleepers. For heavy mineral its 80 pretty much everywhere. I believe there have been numerous studies that indicate freights with an average speed of 80-90km/hr is typically optimum. For Tasrail, its not about the top speed its the average speed. Focus on the low speeds, they are the real money burners, but otherwise 80km/hr for NG on steel sleepers and average weight rail is probably the most cost effective outcome.
Think about the difference between 100 capable and 80, its not much and over 300km, you still spend more time loading and unloading the train the driving it. I heavily doubt there is a viable freight market for rail to get goods from Hobart to L'ton in 2hr, 3hr to BB or NW coast in 3-4hr. This is really the home of the door to door truck express delivery market.
Judging future needs by current standards is whats plagued Australia's retarded railway development since the beginning. By the time there was any serious prospect of getting Tasmania rail network speed average up to the 100kmh mark (the prospects of that are years in the future), the standard gauge network should (hopefully) have advanced to a standard where average speeds have got to the 140kmh mark, hence considering that sort of speed improvement on narrow gauge (whether here or Queensland) as unrealistic is short-sighted. Continuous far sighted and ambitious improvements will act like a magnet to traffic growth to rail, whilst the heavy truck industry crumbles under fair competition and the eventual loss of its years of feather-bedded subsidised advantage.
Most other transport modes have always encouraged visionarys that seek radical future improvements. Rail (in this country especially) has a bad history of regressively resisting radical improvement, remaining satisfied with minor improvements on current restrictive standards. Hence, the sorry history of rail "advancement" in Australia, includes pathetic developments such as;
* the failure to correct the gauge muddle prior to the turn of the century;
* utilisation of ludicrously light rail for years beyond which it was already causing issues with axle-loads (still an issue today);
* long sleeper spacings and minimal if any ballast;
* bridges that would hardly hold up a wheelbarrow;
* the continued forced utilisation of light and feeble locomotives due to the incapability of addressing the points above (again, still an issue today);
* the failure to replace light and weak steam locomotives years after they were totally obsolete;
* the concurrent excessively long utilisation of light, useless 4 wheel wagons anywhere from decades to over half a century from when they should have been banished to history;
* resultant, short, light and inefficent trains and short and useless loops;
* a restrictive loading gauge in far too many parts of the country;
* dieselisation and the elimination of steam at least 20 years after diesels were proven as viable motive power;
........and the list goes on.
Admittedly, there were some rare visionarys in the historic rail industry, such as S.A.R.'s Webb and V.R.'s Clapp. However, these men's efforts were generally stymied by Australia's conservative political system and blind adherence to 'Mother Britain'.
The issues with Australia's regressive rail development is a matter of history and been well explained by the culture of Australia at the time. However, there is no excuse to remain in that mindset these days - at least from the rail industry itself.
My hope is if any of the Inland rail proposals ever get up, the minimum standards should be full U.S. standard axle loadings, loading guage and provision for at least 140kph for freight (regardless whether it was initially needed) and those standards eventually work their way throughout the rest of the D.I.R.N.
Thus my ambitions for the eventual transformation of the Tasmanian network. Realistically, I will probably not see it in my lifetime, but it's a worthwhile aspiration.