Motorists who currently drive for free on the M4 will be paying a toll of up to $4 a trip when the road is widened in four years, the O'Farrell government announced on Thursday.
The widening of the M4 between Church Street, Parramatta and Homebush Bay Drive from three lanes in each direction to four will be the first stage of the WestConnex motorway project. It is expected to be finished by early 2017.
When it is finished, motorists will be charged according to how far they drive along the M4. The toll will range from about $1.50 to $3.90 in today's money, though the cost of that will increase with inflation.
The average toll is expected to be about $3, the government said in a summary of the business case for the WestConnex motorway, released on Thursday by Premier Barry O'Farrell and Roads Minister Duncan Gay, who were accompanied by Prime Minister Tony Abbott and Deputy Prime Minister Warren Truss.
The second section of the WestConnex to be built will be three-lane tunnels in each direction between Homebush Bay Drive and the City West Link. Construction of this section will start in mid-2016 and it will be open to traffic in early 2019.
Later sections of the WestConnex will be another M5 East tunnel linking to St Peters and a tunnel between Haberfield and St Peters, taking the total cost of the project to $11.5 billion.
"This is the biggest single roads project in NSW history," Mr Gay said.
Other details to emerge from the business case summary and press conference include:
The total motorway will have a capped toll of $7.35 in 2013 dollars, though that will increase with inflation.
The government will consider removing general traffic lanes from Parramatta Road, under which the new tunnel will be built. But it says any change to the surface of the road will be subject to community consultation.
The government has announced $200 million for the "revitalisation" of Parramatta Road, but does not have detailed plans about how that money would be spent. Mr O'Farrell said it would be spent on "new footpaths, green space, bus lanes, trees and the removal of power poles".
Parts of Parramatta Road will be rezoned to attract high-density apartments and businesses, though there is little detail yet on where and when.
Bus lanes will be extended along Parramatta Road from Leichhardt to Burwood.
The tunnel between Homebush and Ashfield will require exhaust stacks, but the government is not yet saying where they would be. Mr Gay said an "expert committee" would examine exhaust stacks.
The government is not releasing forecasts of how many motorists would be expected to use the motorway or the different sections of the motorway.
Mr Gay rejected the idea that building a three-lane tunnel to Ashfield would cause a bottleneck at the City West Link, which is two lanes in each direction.
Despite the fact that there are no detailed traffic forecasts, the Roads Minister said "60 per cent of the traffic leaves before it gets to City West Link".
"There will not be a ... huge increase in the amount of traffic using City West Link," Mr Gay said.
The government has also significantly changed its plans for the later sections of the motorway. For example, earlier maps for the WestConnex said a tunnel would extend as far east as Sydney University. But the tunnel now extends only to Stanmore, before turning south to St Peters.
The business model for the WestConnex model differs from previous toll roads in Sydney because the government is planning to fund the bulk of early construction, before selling the motorway off to the private sector once it is open for traffic.
This means private firms will not have to try and estimate the amount of traffic using the road.
But neither is the government releasing its own estimates of how many motorists will use the motorway at any time.
The government has, however, released estimations of significant travel time savings when WestConnex is finished. It says motorists driving between Parramatta Road and the airport will save 40 minutes, and motorists driving between the CBD and Parramatta will save 25 minutes.