I live on the Western side of Melbourne. So, my observations are from this area.
There are many "new limits" of speed in the area - that new limit is to make it slower, not faster.
Many moons ago, the Government at the time was trying to get the State out of indebtedness.
As part of their "safety" initiative, they also reviewed speed limits and lowered them.
The next step was having an abundance of speed cameras to catch "speeders" and raise revenue.
So, be warned, keep your eye on this "New Limit".
Ironically, after that failed Government was removed, the new Government, raised speed limits to keep business moving.
History may repeat!