The South Australian Government on Wednesday announced plans to duplicate and "end the farcical one-way regime of the Southern Expressway" to enable traffic to flow both ways.
The $445 million project will duplicate the Southern Expressway and include a new interchange at Darlington.
Construction is due to begin at the end of next year and expected to be completed in mid-2014.
The 20 kilometre road was opened in 2001 and allows commuters to travel from the city's southern suburbs in the morning. The direction is reversed in the afternoon to allow traffic to flow from the city to the south.
SA Premier Mike Rann criticised the Southern Expressway as a "perfect example of an 'interim measure' that was badly planned, poorly designed and hugely expensive to fix," adding that "duplication of this expressway was an inevitable project that this Government has brought forward so that we can integrate our transport infrastructure, without wasting millions on interim measures."