the police tend to allow 10-15% over or under the speed to allow for miscalculations and the accuracy of the cars odometer and the radar gun. or something like that, my dad told me that neway he is an ex driving instructor XD, can't beat free daily lessons with an experienced instructor.
oh and btw the fastest i've gone is 185-195 near rookwood cemetery, in a friends 2006 model ford XR8. Was AWESOME from 0 to 180 in less then 10 seconds, goddamn i'll never forget that, and i had just gotten my L's. 1337