Last week Transport Minister Mark Bailey used a Mount Isa visit to announce Queensland Rail would look at enabling double-stacked trains to run from Mount Isa to Stuart and potentially to the Port of Townsville, with a business case finalised this year to work out the cost and demand for double stacking, where trains can carry two layers of freight.

He then told parliament it was one of three projects on the rail line as part of a $50 million investment.

However the Brisbane-based Rail Back on Track group which promotes the use of rail as an alternative road has its doubts it is possible.

The group's Robert Dow said that while they welcomed the Palaszczuk Government's $50 million investment in the line they doubted the business case would stack up due to technical reasons.

"The Townsville - Mount Isa railway is 1067 mm ( 3' 6" gauge ) and as far as we can determine there is no railway system in the world of 1067 mm gauge that runs double stacked trains," Mr Dow said.

"The 1067 mm gauge is too narrow for stability, and the rail weight limits on the line are presently 20 tonne axle load (tal) and this will not allow for heavy double stacked trains in any case, of mineral concentrates, refined metals and so forth."

Mr Dow said the maximum train length was also constrained by the length of passing loops.

"Of the 46 passing loops the shortest loop is at Marathon at 1009 metres, but there are many others in the region of 1020-1030 metres or so," he said.

"We are not confident that double stacked trains could be introduced on the Mount Isa to Stuart railway unless the gauge was converted from the present 1067 mm to 1435 mm (standard gauge) and the rail weight increased to allow trains with at least 25-30 tal."

Mr Dow said without this the business case for double stacked trains was just a waste of Queensland taxpayers' money.

"Money is better spent on lengthening passing loops and replacing the existing lighter sections of rail, and improving the track stability so that the lower speed restrictions can be removed," he said.

The other projects planned on the line including improving flood resilience on the line and the replacement of ageing rail equipment like sleepers and ballast.

QR will start geotechnical and survey work this month, to pave the way for the installation of new bridges and the replacement of culverts with spans and new piers to significantly increase capacity on waterway openings and provide protection to embankments to better withstand flood events.

It adds to $6 million in works already underway to bolster flood resilience between Cloncurry and Hughenden.

Mr Bailey also said $20 million of the state government's $80 million, four-year plan to encourage freight operators to use the rail line had been accessed.

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