The RTA proposed most of the restrictions on traffic from the east accessing the Harbour crossings and the Domain Tunnel at the Supplementary EIS stage. The Supplementary EIS report says this is 'due to increased traffic volumes forecast under the Modified Activity' (i.e. the 'Long 80' proposal). In other words, the DoP accepted the very high initial traffic forecasts in the CCM proposal and the RTA-commissioned patronage study.
The strategy behind the DoP Conditions of Approval was to restrict the use of roads from the east giving access to the Domain Tunnel and Sydney Harbour crossings. The RTA would implement these road changes immediately upon the opening of the tunnel. This was to make travel on alternative surface roads unattractive for motorists wishing to avoid the toll, and prevent any 'induced traffic' effects.
Perhaps this is an area which was not well understood by the public. The CCT project was used to improve amenity throughout Central Sydney. Its aim was to get motorists off surface streets and into the tunnel. The forecast number of vehicles that would use the tunnel was the critical factor in deciding the necessary road changes.
The RTA developed and implemented the road changes based on its revised forecast patronage for the longer tunnel. This forecast gave a picture of 82,347 vehicles a day using the tunnel in the first year, leaving the surface alternative routes relatively free. If this was correct, the logic of restricting roads to prevent the 'induced traffic' effects would also be correct.