The federal government is kicking in almost one billion dollars to fast-track work on Adelaide's North-South road corridor.
A total of $1.5 billion will be spent on the project – with the South Australian government contributing $572 million – so construction work can start next year.
In a joint statement, the state and commonwealth governments said the investment meant construction work could be done on two sections of the road at once.
The works will include upgrading the existing Darlington Interchange to expressway standard and widening South Road between Torrens Road and River Torrens.
The upgraded roads are expected to be open to traffic in 2018/19.