Great desciption from christopher
The one thing we'll emphasise is that speed limits are enforced more strictly in aus than any other country in the world and also if you are unfortunate enough to drive in Victoria show extra care as the speed cameras are set with only the most minimal tolerence (about 3kmh) and they use average speed cameras on the main freeways. If you are planning some long distance driving in aus I'd strongly recommend hiring a car with cruise control