Traffic congestion will ease and hundreds of heavy vehicles will be taken off one of Sydney's busier commuter routes with a long-promised "missing" roads link, the NSW and federal governments say.
The governments on Sunday reiterated a commitment of $405 million each to the $3 billion NorthConnex project, with twin tunnels to link the M1 and M2 motorways.
However, the federal opposition called Prime Minister Tony Abbott a "pretender" for announcing a project his predecessors agreed on last June.
Construction of the nine-kilometre tunnels will start next year and the road link is scheduled to be open to motorists by 2019.
The state and federal governments say NorthConnex will ease traffic congestion along Pennant Hills Road and allow travellers to bypass 21 sets of traffic lights.
It is also tipped to pull more than 5000 trucks a day off the road.
"Generations of people said they were going to build it but they haven't," NSW Roads Minister Duncan Gay told media on Sunday.
NSW Premier Barry O'Farrell said the link would be a quicker alternative for trips to the Central Coast, the Hunter and the Sydney city centre.
"A truck, for instance, leaving the Port of Newcastle (could) go all the way to Melbourne without going through a set of traffic lights," he said.
A $6.11 toll for cars and $18.32 for trucks will contribute to the project costs.
Shadow infrastructure spokesman Anthony Albanese said Labor and the O'Farrell government agreed in 2013 to put $405 million each on the table for NorthConnex.
But Mr Abbott said nothing much ever happened under the former government.
"This is now on the high road to construction and completion in a way you could never be sure of under the former government in Canberra," he said.
Lend Lease and Bouygues are the preferred tenderers to design and build the motorway, overseen by Transurban.
Mr Albanese said Mr Abbott hadn't contributing anything to the project.
"Not a new dollar, not a new metre of road, no involvement whatsoever," he told reporters in Sydney after the prime minister's announcement.
Building the NorthConnex will significantly reduce congestion and help deal with future traffic growth, NRMA president Wendy Machin said in a statement.
"Anyone who has headed out of Sydney on a public holiday knows just how desperately Sydney needs NorthConnex," she said.
"This missing link will alleviate traffic on Pennant Hills Rd and the Pacific Highway and the improvements to freight delivery will be significant."