The freeway extension, which would run from Waterfall through to Tempe and the airport, is understood to be one of the key initiatives in a NSW draft transport master plan soon to be released by the government.

"The release of the draft long-term master plan is imminent," a Transport for NSW spokesman said.

"Once it is released we will be seeking further input from the public and industry before settling on a final plan at the end of the year."

NRMA deputy president Michael Tynan, who has been lobbying governments for the extension for more than seven years, said he was "very optimistic" that it would finally get the go-ahead.

"It's positive stuff," Mr Tynan said of the news.

"It's not yet there by a long shot but ... it's the most positive thing I've heard in my time of chasing the F6 extension."

Mr Tynan said the extension would also be welcome news for Illawarra residents driving to Sydney for work, as it would slash travel time and frustration.

"At the moment there's something like 14 per cent of the Illawarra's working population who travel to the Sydney metropolitan area every day," Mr Tynan said.

"They use the F6 as it is now. As soon as they hit Waterfall they slow right down, and as they get closer to Sutherland it becomes a disaster.

"And then of course, a lot of people will travel further, along the Princes Highway or General Holmes Drive to the airport. We only need to have one hiccup somewhere and it's at least an hour's delay."

Mr Tynan said the extension would help alleviate the traffic snarls that were expected at the northern end with the increases in truck movements from the enlarged Port Botany terminal.

The extension has been on the drawing board since at least 1951, when a corridor of land was set aside for the motorway.

While the route of any extension has yet to be released by the government, Mr Tynan said the NRMA had a good idea of where it would go.

"We believe we know the route because all the land is still there, right through to the airport.

"Unless they change the route, I don't know, but that would seem an enormous dislocation to a lot of people when the actual route is still there.

"There are a lot of playing fields on it now - recreational areas - and a lot of it is just green grass," Mr Tynan said.

Heathcote MP Lee Evans has not seen the master plan but believes an F6 extension would be a great benefit for the South Coast and southern Sydney.

"The guesstimates are of about 20 to 25 minutes being cut off the trip," Mr Evans said.

"So it would be a fantastic thing if we could get it planned and built."

He said sitting back and doing nothing was not an option.

"We're going to have to do something for traffic coming from the south.

"If the F6 extension does not go ahead we've got to do something about smoothing the traffic out, whether it be underpasses or overpasses or whatever.

"We need to do something to keep the traffic flowing, otherwise in another five to 10 years it's going to be grinding to a sickening halt," he said.