Drivers from western Sydney will get a shorter trip to the city for less if the tunnel linking the M4 and M5 tollways is approved, according to the just-released environmental impact statement (EIS).

It says that at present a driver can pay $22 in tolls for the 55-kilometre trip from Penrith to Sydney's CBD.

If the link is approved, it says tolls will be capped at $8.60 and the trip using the M4 direct to the City will be shortened by 15 kilometres.

The $7 billion link runs underground for about 8 kilometres, connecting the M4 at Haberfield to the St Peters Interchange, via another interchange at Rozelle.

'High risk of dust impacts'

If construction begins next year as planned, it will be the start of five years of disruption for those living near the project's main construction sites.

Apart from noise, thousands of truck movements and congestion on local roads, the EIS identifies dust from construction activities as one of the main risks for human health. It says:

"There would be a high risk of dust impacts associated with activities in Rozelle, in particular demolition works."

The EIS outlines several ways to mitigate the exposure of residents to dust and heavy vehicle movements.

The report also forecasts increased traffic congestion where the link meets surface roads.

This would affect parts of Mascot, Frederick Street at Haberfield, Victoria Road north of the Iron Cove Bridge, Johnston Street at Annandale and the Western Distributor.

Design and construction approach indicative only

The route for the tunnel under Sydney's inner-west that will link the M4 and M5 as part of the WestConnex Motorway was released on May 12, 2017. ( Supplied: NSW Government )

There appears to be a caveat over the design and construction details contained in the EIS.

It says that unlike the other sections of WestConnex, the M4-M5 link contractors will undertake detailed design and construction planning "after" the project is approved.

"This means the detail of the design and construction approach presented in this EIS is indicative only."

Asked about the change in approach, Planning Minister Anthony Roberts said the community's views would be taken into account.

"I welcome any opportunity for the community to get involved in Government decision making, and that's why we have this process where people are able to put in submissions," he said.

"...if you're interested, if you have issues, take the time to put a submission in and that's why we've kept it open for a couple of months."

Approval process a farce: Greens

The Greens have accused the NSW Government of rushing through the approval process.

Greens MP Jamie Parker, whose seat of Balmain will host three exhaust towers and an interchange, said the process was a farce.

"They're pushing off so many of the important details to the contractors and that can't give the people of Sydney any security about the impact of this development or the true cost of this proposal," he said.

"For the first time we see traffic modelling demonstrate there'll be even more traffic, as a result of building WestConnex, along areas of Victoria Road, in Annandale, along the Western Distributor to ANZAC Bridge in Haberfield, Mascot and more.

"This project just merely pushes traffic around to the next bottle neck and doesn't solve the problem. Only world class public transport can really reduce demand for our roads."