Its really simple - if you don't want to get caught speeding then don't speed. If you like to speed then when you get caught don't bleat about it.
As for the A9 - if you cannot tell when it goes from dual carriageway to single then you shouldn't be driving. The presence or absence of a central reservation , the large signs that are in place 1/4 mile before the end of the dual and again at the end of it and the speed limit signs are a clue.
Speed if you want and it is safe to do so - I often do - but if you get caught - especially if your observation is lacking then do not bleat about it.
