I would offer an alternative view.
That is speed signs. Here at least in Australia, the speed signs in Australia are set at the lowest common denominator, not the highest.
That is they are set at the "safest" level, not at what "most" people would consider acceptable.
In these days of litigation and law suites, where everyone else is to blame, do you blame THEM, for erring on the safer side?
I don't even though I personally agree with Spacephantom's view of Totem's conservatism, therefore I will support their stance AND I have heard all the arguements.