There was nobody to zoom you past... mostly road trains and some caravans on the road, which are slow anyway..... only just in the beginning of journey near Kellerberin WA, a V8 Holdon Commodore passed us quite fast, my estimate would be somewhere 180~200km/h... else folks here take speed limits seriously... in Dubai we could do 140km/h in a 120km/h, even 160km/h without camera flashing (once upon a time), here if you are even 5km above limit, you get it with demerit points 
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I never exceeded 120km/h ... but there were a couple of places where I had to push to 140km/h to pass a 54m road train... if I had no load and/or a powerful sedan, I'd have pushed it to the limits atleast once to see how it goes ... and by the way, the only police I saw during this trip were mostly in NSW region, nothing in WA, a couple of them maybe in SA and VIC... and thats it..
