Longer motorway to ease Adelaide traffic

A non-stop motorway to ease traffic congestion in Adelaide's south is to be extended.

The federal and South Australian governments have awarded the tender for the $896 million project to an alliance made up of Leighton Contractors, Aurecon Australia and York Civil.

Under the deal the length of the non-stop motorway along South Road will increase by 600 metres to three kilometres, including the addition of an extra underpass.

Federal Assistant Infrastructure Minister Jamie Briggs says the improved project will not cost taxpayers more than originally planned after a competitive tender process.

Mr Briggs says the project will create jobs and drive economic growth by improving Adelaide's transport network.

South Australian Transport Minister Stephen Mullighan says the number of vehicles using South Road will more than double to 115,000 a day once the motorway is completed in late 2018.