They need to just get on with this already.
They'll be spending over $10 billion if the government is to be believed hence the delays. That's almost $1 billion per kilometre.
For that money they could buy up all the properties along that stretch and dig a trench the whole way, and still have money to help businesses relocate.
Tunnels or a single long tunnel would be cool, but let's be realistic.
Forget the heritage excuses. What heritage? Who gives a shit about some old houses. They wont be standing in 200 years let alone 500 years, it's not like in centuries to come our descendants will be looking at them as ancient monuments with tourists visiting them like we do with the Pyramids and so on, they wont give a shit about some old houses, majority of people today don't give a shit, so why hinder progress and drive up the cost of getting shit done?
Just bulldoze everything along the remainder of the corridor that can't be worked around at a reasonable cost, dig out a trench and get it done.
Any other city would have been all over this by now. Only SA with it's backwater minded politicians still pissfarts around with how to upgrade a road.