The operational agreement behind “ramp meters” that slow down cars passing through Sydney’s controversial $4 billion Rozelle Interchange cannot be made public because it involved “significant commercial negotiation”, AFR Weekend has been told.

The opening of the Rozelle Interchange, a network of underground toll roads, in November created fury among Sydney motorists because free above-ground roads leading into Sydney’s city centre via the Anzac Bridge were changed, creating dreadful traffic congestion.