The speed limits in Australia are far too draconian, if you stick to the mandatory speed limits when overtaking you would stand a good chance of being killed or involved in a head-on collision. Australians are not taught how to overtake and the law as it stands does not permit safe overtaking, if you overtake a lorry or a car that speeds up, and you have to exceed the speed limit you can and will be done for speeding, it appears the Police have no discretion or prefer to not use their powers of discretion as they obviously get brownie points the more they can catch.