The minister's comments follow a decision in the Northern Territory where motorists were permanently allowed to choose their own speed along a 276-kilometre section of highway following a successful 18 month evidence-based trial.

In a decision condemned by medical authorities, Territory Chief Minister Adam Giles on Thursday released a report confirming that no speed limit had reduced the number of accidents along the trial section of the Stuart Highway when compared with a 130km/h posting previously in place.

In NSW, Mr Gay has ordered Roads and Maritime Services to cost remediation works on both the Pacific and Hume Highways which would mandate grade-separated intersections and crossroads.

"We're OK at 110km/h but when you've got crossroads coming in on most of those roads . . . that's a problem," Mr Gay said. "The best way I can look at raising the speed limits in place is to put a proper road in to allow that [to] happen . . . I'm awaiting the results of those costings shortly."

Minister Giles in the Northern Territory confirmed a new 60-kilometre extension that will stretch the de-restricted zone to 336 kilometres between Alice Springs and the Ali Curung rail overpass. The developments follow a $4.4 million investment from the Territory government on upgrading the Stuart Highway to suit higher speeds.

"Driver safety has always been paramount during the trial and the sections of the Stuart Highway selected were chosen because they represented the least risk and lowest crash statistics," Mr Giles said.

"The traffic counter data shows there was only a small increase in driver speed in the trial sections, with 85 per cent of drivers travelling between 133 and 139 kilometres an hour."

The report found the fastest speed admitted to by a driver was 295km/h. Prior to no speed limit, the average speed in the trial area was 134km/h, with the highest speed registered at 205km/h. Car makers including Porsche have returned to the Territory to conduct testing since the open speed trial commenced, pushing its 918 hypercar to 350km/h.

Whereas most Australian states have pursued lower speed limits in recent years, the Territory example provides an interesting case study.

Open speed zones were abolished by the former Territory Labor government in 2006 and replaced by a limit of 130km/h. More people died on Territory roads (307) in the six years after, than in the six years before the change (292). Moreover, countries such as Germany, the Netherlands, Spain and Denmark record lower annual traffic deaths than Australia despite featuring speed limits of 130km/h or higher.

The Territory government announced a $2.5 million upgrade to coincide with Thursday's 60-kilometre extension.

Stakeholders believe clearing trees away from the edge of the highway, widening curves and improving the marking and signage not only reduces accidents, but helps eliminate fatigue.

Originally published as 120km/h speed limit for freeways under review by Newcastle Herald.