Locals have dubbed the former intersection blackspot, "Six Star Junction" because of the seemingly high cost of the project funded by State and Federal governments to resolve a long history of major road accidents and fatalities.

Member for Charlton, Greg Combet, was a prime mover in the project making good a pre-election promise to fix several accident blackspots in the Charlton electorate.

A spokesperson for Mr Combet said the original cost of the new Rathmines roundabout included the cost of moving the transformer so a slip road could be constructed to enable through traffic to by-pass the roundabout.

"It isn't a matter of who is going to pay to move the transformer, it is a matter of when Energy Australia can physically do it because while it is an RTA road, the RTA aren't electrical contractors," the spokesperson said.

"Mr Combet has been told that moving the transformer is now imminent and when that happens the slip road can be finished and opened to traffic," the spokesperson said.

Energy Australia spokesperson, Allan Hamonnet, said design work to relocate the system was already in progress.

"Moving the unit has been prioritised," Mr Hammonet said.

Together with a $1 million upgrade of the Donnelly and Wangi roads junction at neighbouring Wangi Wangi, the two projects account for the lion's share of Federal Government's $5.4 million to fix 14 blackspots in Mr Combet's electorate since he won the seat in November 2007.