Victorian motorists will pay extra tolls until 2045 to cover part of the cost of the $6.7 billion West Gate Tunnel - but they won't be told how much it will cost them.
Construction on the new freeway will start next month after contracts with builders CPB/John Holland and tolling company Transurban were finalised on Monday.
"If we don't build this road, well it's unthinkable what will happen to our economy," Premier Daniel Andrews told reporters on Tuesday.
Transurban will fund part of the road's construction in return for an extra 10 years of tolls on CityLink, meaning motorists will pay tolls on a different road until 2045.
But the premier and Treasurer Tim Pallas would not say how much money Transurban will reap from the 10-year extension.
"These arrangements are cheaper, from a motorist's point of view, than the arrangements put forward by the previous government," Mr Andrews said.
Mr Pallas said he would leave it to others to do the maths on how much motorists will pay over 10 years.
The West Gate Tunnel was meant to cost $5.5 billion when Transurban took the proposal to Labor in 2014, but will now cost $6.7 billion as the tunnels are now twice as long as originally planned.
The project was not taken to the 2014 election, but shortly afterwards Labor announced it would replace its $500 million plan to get trucks off suburban streets in western Melbourne.
Early works will begin in January, with two tunnel boring machines ordered in coming weeks, and the project is expected to be completed in 2022.
