The Northern Territory Government plans to expand its trial of removing speed limits on major highways.

Two months ago it removed the speed limit on a 200-kilometre stretch of the Stuart Highway between Alice Springs and the Barrow Creek area, as part of a 12-month trial.

Northern Territory transport minister Peter Styles now wants to go further.

"We're looking at various sections of road, both on the Stuart Highway and on the Barkley Highway that may be available to open up as part of the trial," he said.

"I believe it's been a success so far. Anecdotal evidence that I've received is that people are behaving themselves.

"We've always said and [told] people that it's their responsibility to drive to the conditions of the road, the condition of their vehicle, to their own capabilities.

"Generally, most people have. The police have indicated that everyone seems to be doing the right thing out there.

"The truckies that we've spoken to and the trucking people have said that they're very pleased."

YouTube videos suggest some drivers have reached speeds of 250 kilometres per hour.

NT roads not suitable for high speeds: expert

The policy of no speed limits on major highways was an election promise. If it is officially adopted it will reverse the abolition of speed limit-free roads in 2007.

Road safety experts condemned the trial when it began and its success so far has not convinced them.

Ian Faulks, a researcher with the Centre for Accident Research and Road Safety at the Queensland University of Technology, says Territory roads are not suitable for very high speeds.

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"It's not the kind of road that's like an autobahn where you would want to go really fast," he said.

"I think it has been something very positive in terms of the Australian driving population in that they haven't been silly and haven't gone for very high speeds."

Mr Faulks believes the lack of disastrous events proves that drivers are more sensible than the NT Government.

He says expanding the 12 month trial so soon after it has started makes little sense.

"Any decision to actually introduce further stretches of Northern Territory highway to a no-speed-limit policy are really based on anecdotal information," he said.

"That's not good enough; we really should be trying as much as possible to base it on really good data and really good evidence."

Final decision a long way off: NT minister

The trial is based on the reports of four consultants.

The ABC's attempt to obtain the reports, through a Freedom of Information request, was rebuffed by the NT Government on the basis that releasing the reports would breach Cabinet confidentiality.

Five invoices totalling nearly $140,000 up to May last year were provided but these give no clues about the work involved.

Mr Styles says the advice is essential as the Government decides whether the trial becomes permanent.

"That won't happen until the final audits and assessments are done," he said.

"From those audits and assessments that have been done across the national highway network in the Territory, there will be a report pulled together from all of that information and that'll go to government for its consideration to decide, will we have open speed limits again?

"Will we not? Will it be restricted to a certain part of the highway? We're a long way from that decision."