THE $1.7 billion handshake guaranteeing the entire cost of the Toowoomba bypass would have State and Federal funding was made a day before politicians took their Christmas leave.

Months of backroom haggling between the two political tiers were finally resolved when Queensland Treasurer Tim Nicholls put $342 million on the table.

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He wrote to Deputy Prime Minister Warren Truss in December to tell him Queensland would commit to 20 per cent of the project's total cost if the Commonwealth agreed to pay the $1.36 billion shortfall.

Accountants went into overdrive to find the $636 million needed to almost double the Federal Government's original $700 million outlay.

Announcing $1.7 billion in funding for the Toowoomba bypass are (from left) John McVeigh, Paul Antonio, Ian Rickuss, Scott Emerson, Jeff Seeney, Warren Truss, Trevor Watts, Ian Macfarlane and Tim Nicholls. Bev Lacey

"We said, 'the deal is 80%-20%, here's our 20% on the table ($342 million) and we're right to go'," Mr Nicholls said.

"The day before I went on Christmas leave, the Federal Government came up with the extra funds to commit to a $1.36 billion share."

Cottesloe Park was brimming with suits yesterday as the official Toowoomba bypass funding announcement was made.

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Strong applause for Member for Groom Ian Macfarlane - even a "three cheers for the government" led by Toowoomba Regional Councillor John Gouldson - blended with the clatter of trucks descending the range.

It is a sound Mr Macfarlane says will be nought but a memory once the bypass has been completed in 2017.

"There were doubters, but there was absolutely no doubt in my mind," he beamed.

Bypass 3D Flyover: A 3D flyover of the new route of the proposed Toowoomba Bypass.

The private sector was invited to register interest in building the 41km road within an hour of the announcement.

The government expects about a dozen different consortia to enrol on the interest list, which will then be whittled down to four or five key players.

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Deputy Prime Minister Warren Truss said the project would "move quickly" to an expression-of-interest phase, in which the private-sector frontrunners would present their business cases.

"A successful contractor will be named later this year, with construction expected to begin by mid-2015," he said.

"The successful proponent will be responsible for the design, construction, financing of the new bypass, as well as for the operations and maintenance, including the collection of toll money."

Jeff Seeney, Warren Truss and Tim Nicholls make yesterday's announcement at Cottesloe Park. Bev Lacey

Yesterday's announcement has committed the Federal and State Governments to sharing the cost deficit in an 80% to 20% ratio.

The creation of business cases is expected to cost each group between $5 million and $10 million.

Those outlays are likely to be either partially or wholly subsidised by the government, potentially costing $50 million before any construction plan has been chosen.

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Mr Nicholls said it was a necessary sacrifice to ensure competing companies weren't scared off by the money they stood to lose.

"We want the best companies with the best plans," he said.

Tolls for passenger vehicles and heavy transport will apply to the new road, though costs have not yet been decided.

The Queensland Trucking Association said drivers would be willing to pay a toll up to $25.

A toll on trucks will also be applied to the current Toowoomba Range road.

The bypass is expected to take 30 to 40 minutes off the total travel time across the range for heavy vehicles, eliminating 16 traffic lights along the way.