The trial was initially launched in February last year with a 204km section between Alice Springs and Barrow Creek, but September saw that extended by 76km to just south of the Ali Curung Rail Overpass.
The trial has so far proven an injury- and hoon-free exercise, with a year-long government survey finding that most road users travelling along the stretch have maintained speeds below 140km/h.
This week, NT transport minister Peter Chandler has revealed plans to propose another extension of the open speed limit, pending the approval of necessary road works.
It is hoped that the results of a report into the trial, which will not be released to the public due to a cabinet-in-confidence ruling, will see the open speed limit expanded to include more sections of the Stuart Highway and a stretch of the Barkly Highway.
"There are sections that, with a little bit of work, some additional signage, some widening of corners and so forth, could be brought up to a level where you could go to an open speed limit," Mr Chandler told the ABC this week.
Similar works have already been carried out as part of the existing trial, with around $1.55 million spent on safety improvements and new signage.
The spend, and this latest proposal, has drawn criticism from the NT Road Transport Association.
"Our question is whether [expanding open speed limits] is the highest priority in terms of the NT road infrastructure budget," NTRTA executive office Louise Billato told ABC Radio in Alice Springs this week.
"Do we really need to be putting ourselves into a situation of channelling multi-millions of dollars to keep the road safe so that a few people can drive at very fast speeds?"
NSW roads minister Duncan Gay has confirmed that speed limits on the Hume and Pacific highways will be reviewed again once major safety works have been completed by around 2020.