The current duplication of stage one from the ACT border towards Murrumbateman means the existing carriageway next to the trees would become southbound while the new northbound lanes will be built on the other side of the trees, leaving them in the middle of both carriageways.

The current design comes after the Onerwal Local Aboriginal Land Council and various ACT and Yass Valley environmental advocates lobbied the Barton Highway Upgrade Alliance, which is part of Transport NSW, to not proceed with its first design that involves removing the trees altogether.

Ngunnawal Elder Wally Bell said the redesign - just past the Victoria Street parking area in Hall - after the council lobbied for changes was a "tokenistic effort".

"We noted that we had these scarred and ring trees, which are rarer," Mr Bell said.

"In relation to what they've come up with here, to me it's a very tokenistic approach.

"They're looking at this little island between the two big roads.

"Works are going to impact underneath the gridline, which will probably have some effects on the trees. It's probably going to kill them."

Mr Bell said the redesign showed a lack of understanding of Indigenous cultures.

"Further up near Kaveneys Road, there are more scarred trees there and what we call our circle trees, which are spiritual," he said.

"Our culture is both physical and spiritual - that's where people have to try to get a better understanding of what we talk about regarding our connection to the country.

"We have a strong belief that we all come from the land itself and that's why we in turn look after the land."

Stage one works officially started in November 2020 after the Australian and NSW governments provided $50 million each to fund the stage, which the Barton Highway Improvement Strategy 2017 identified as needing immediate works.

The Australian Government has committed a further $100 million, pending further planning.

As part of the stage, a significant area of the Hall travelling stock reserves is being cleared to make way for the northbound carriageway.

Ginninderra Catchment Group's treasurer John Connelly said he along with the land council and other agencies, including the Yass Area Network of Landcare Groups, had been consulting with the BHUA "for some months to alter the design".

Mr Connelly said a "proposed community option" is to build the duplication in the space between the trees and the existing highway, which would need only a small amount of clearing and would retain road geometry from the ACT.

"We have provided them with what in our view is a very acceptable alternative road alignment that does not involve any clearing of the Hall TSR and leaves the ring tree contiguous with the rest of the Hall TSR," Mr Connelly said.

"However, so far the BHUA has steadfastly refused to consider any alteration of their road design.

"They have failed to give any reasons why our alternative design is not acceptable.

"They simply do not address that question but doggedly repeat that their option is the only acceptable alignment."

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Mr Connelly said the BHUA's response to the question about the alternative design was citing the fact they gained approval for the road design under the EPA Act.

He also said it continually referred to its review of environmental factors, which admits its preferred design out of numerous options was the least environmentally friendly.

"While this option has the greatest impact to the Box Gum Woodland on the western side of the highway, it provides adequate space for future proposals to upgrade the existing highway," the report states.

"This option minimises impact to traffic during construction and would provide a safer design for road users."

Mr Connelly said a "submissions report" was prepared but those making submissions, including himself and various groups, were not notified of the report's publication.

He said BHUA stuck to the original road design despite submissions showing other alternatives that avoid clearing the Hall TSR and destroying a homestead.

Sonya Duus, president of the Yass Area Network, said the ecological and heritage values were "really important to get right".

"It's also about setting up a precedent for how we operate in the later stages into NSW," Ms Duus said.

"We're concerned about this area, but we're also really interested in setting up a working relationship and a good precedent for later one."

In its May update, Transport NSW said it was committed to "preserving Aboriginal cultural heritage and recognises the impacts of the Barton Highway upgrade".

"During the environmental studies for the first stage of the project, 11 Aboriginal archaeological cultural sites were recognised, including two ring trees identified within the construction boundary," it stated.

"Surface collection work was recently carried out to identify and salvage any items of Aboriginal significance."

Southern NSW Transport director Sam Knight said specialist road designers had delivered "a high standard of alignment while protecting culturally significant trees, minimising impacts to ecological communities in the Hall TSR and complying with AusRoads safety standards".

"Transport for NSW worked in consultation with the local Aboriginal community to refine this design to specifically save two Aboriginal cultural ring trees," Mr Knight said.

"An expert in squirrel gliders has been engaged and nest boxes have been installed in the area."

"Transport for NSW takes its obligations to the environment and the local community seriously and appreciates receiving input and working with individuals such as Mr Connelly and other local community organisations."

Mr Knight said unfortunately the alignment proposed by Mr Connelly would not allow enough width for the two lane divided highway.

He said it would also not allow a safe median distance, would have an impact on the cultural trees and does not comply with a 100 km/h design speed, resulting in a sub-standard road safety outcome.

"Improved safety is a key driver of the Barton Highway Upgrade," he said.

The NSW government said the overall upgrades would improve road safety "while enhancing tourism, driving economic growth and creating vibrant regional spaces".

The stage one works are anticipated to be completed in 2023, weather permitting.

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