That's what Transport for NSW western region director Alistair Lunn says of scepticism that the mammoth project to upgrade the Great Western Highway from Katoomba to Lithgow will actually go ahead.

Community feedback has now closed on the NSW Government's ambitious plans for the highway, which will cut the time taken to travel between Orange and Sydney by about 10 minutes and deliver four lanes from Emu Plains to Wallerawang.

Asked how the people of Bathurst could be sure the upgrade would happen, Mr Lunn pointed to the government's financial commitment.

"This is the first time that really significant dollars have been put against this project," he said. "There is $2.5 billion on the table."

While acknowledging that some aspects of the project were more complicated than others and would take a number of years to complete, Mr Lunn said Transport for NSW was pushing on as "quickly as we can".

He said the Great Western Highway project had the potential, once the Pacific Highway upgrade was finished in 2020, to become the biggest project in regional and outer metropolitan NSW and "a showpiece of road engineering".

"It's incredibly interesting and incredibly challenging," he said.

He said the government would be "able to move quickly in construction" on the highway through the valley and at Medlow Bath in the Blue Mountains.

Early work and construction on some sections of the upgrade is due to begin in 2021.

The upgrade to the Great Western Highway from Katoomba to Lithgow will add to the duplication of the highway through Kelso that was completed in March 2017 and the upgrade of the highway from Kelso to Raglan, which is due to start in 2020.

A concept design for the Kelso to Raglan upgrade - which will provide two lanes each way from Ashworth Drive, at the Big Gold Panner, to Napoleon Street, on the western edge of Raglan; and two lanes eastbound and one lane westbound from Napoleon Street to the east of Ceramic Avenue - was released in July last year and a detailed design is now being prepared.

Early works for the upgrade are expected in the new year.

When the Kelso to Raglan upgrade is completed, Bathurst will have 11.2 kilometres of two lanes of traffic travelling eastbound from the Stewart Street roundabout to west of Glanmire.