Transport for NSW has announced that an estimated 3000 artefacts have been unearthed during archaeological testing along the route of the proposed duplication of the highway.

The work has been carried out in the region since June.

Transport for NSW director west, Alistair Lunn, said the Aboriginal community would consider the best methods of preserving the artefacts.

"The Blue Mountains crossing has strong cultural connections for many groups - including a long history for the Wiradjuri, Gundungurra and Dharug peoples - and this is a key consideration as we continue to plan for the upgrade between Katoomba and Lithgow," Mr Lunn said.

"The artefacts were unearthed during the recent planned excavation of 17 sites to inform the Environmental Impact Assessment process for the highway upgrade.

"Radiocarbon dating and residue analysis are being used to analyse the artefacts, including stone cutting tools and a hearth, but it is expected that some could be up to 5000 years old."

TfNSW has been using specialist archaeological and Aboriginal interpretive consultants to carry out the work. There have also been representatives from the various registered Aboriginal parties (RAP) on site during all of the digs.

The recovered artefacts, including flaked pieces of stone, cores and hammers, are now being kept under lock and key, according to National Parks and Wildlife legislation and Office of Environment and Heritage regulations.

Project archaeologist Andrew Costello said RAP members had the final say in the care and control of the unearthed items and would ultimately decide how they would be stored or displayed in the future.

"Some could be sent to a museum, some of the artefacts could be reburied in an area of landscape as close to possible where they were excavated once the new road is built," Mr Costello said.

"There are lots of rules about provenance with the idea that if someone comes along in 50 years to do more study, there is an agreed method of holding and preserving these artefacts with all of the archaeological data to go with it."

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The digs have revealed many by-products of tool-making, including microblades which as a technique date back around 5000 years.

"The biggest find was an intact hearth from a camp site near Jenolan Caves Road - a camp fire with evidence of stone artefacts and non-human bone," Mr Costello said.

Indigenous people are understood to have used the area to collect and process possums. Mr Costello said some of the tools would be tested for any evidence of possum blood or skin.

"That would match the archaeology to what we're learning about the cultural heritage," he said.

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