A9

I believe this is the longest stretch of trunk road in the country monitored with average speed cameras.
They do exactly what it says on the sign so slowing down at their vicinity alone (and many drivers do that) will do very little to reduce chances of a speeding fine and penalty points.
Their introduction has been controversial and divides the opinion of those considered to be well informed  on the matter. Safety measure or revenue raiser? There continues to be horrific crashes on the route since coming on line and just the other day (tomorrow with respect to this post as I do so late) the road was blocked at Drumochter, a few miles south, forcing traffic to divert on to narrower and less suitable roads .