The NT section of the Stuart Highway had no speed limit until a few years ago. They then introduced a speed limit of 130 km/h (about 81 mph), but found that the rate of accidents went up slightly. Over the past couple of years, after a formal trial, the open speed limit has been returned to much of it.
There are long straight stretches through treeless flatland, where you could see approaching cars or wildlife for miles, so you can wind her up a bit. A bit of pedal also gets you out and around road trains without hanging out on the wrong side of the road for too long. Interestingly, though perhaps not surprisingly, accident rates appear to have gone back down again with the removal of the speed limit. It is some long and boring driving at lower speeds.
FWIW According to the trial report, the highest speed anyone actually admitted to during the trial was 295 kmh (about 184 mph).
Montana discovered the same thing but federal pressure and one dumbarse lawyer has made us have one.
