In the opening scene with the two policemen, a partially deteriorated billboard reading "Golden Fleece" can be seen by the highway. Golden Fleece is an actual name of several companies in Australia.
Western Australia does not have a dedicated highway patrol unit. All law enforcement on WA roads is done by the state police whom use the standard state police decal on their vehicles.
When Mick Taylor shoots the first highway patrol officer you can hear the gunshot before the impact. In fact you'll hear the shots seconds later from the victim's perspective.
Both the highway patrol car in the opening scenes, and the 4x4 as Rutger and Katarina are looking for a ride leaving Wolf Creek Crater (at around 20 mins), bear the same Western Australian license pate 1DUU347.
Mick Taylor: [grabs the sergeant and holds him up against the police car]
Now, your little mate's right, I am a *pig shooter*! Ya know what I do to pigs when they start squealin'? I make 'em stop!