Yes, they do.
Spending all day on the road, however, it becomes obvious that they are not just placed at accident blackspots, but in places where they are sure to get the required number of "hits" needed.
My Wiltshire one was from a corner where a 60 limit turns to 30 after a bend with a pull in 20m after the sign...(where they wait) sign is not visible until you round the bend.
Thats hardly fair..................
And I dont drive like a twat.... see enough people doing that all day long