Canada

In Ontario, they are in fixed places and signage is required ahead of their position. Heck, they are on google maps. Unless you are driving on an empty road, you will know where they are when suddenly everyone slows down, then speeds up again about 20 seconds later. Quebec, on the other hand, is more like Calgary. They do have signs as well, but they move the little vans around. They are pretty conspicuous though, so easy to spot. I wonder if there is any data on their efficacy by deployment. Or maybe it just depends on the individual. I know one guy who got tagged doing 60ish three times in a week in the same spot because he never noticed the new camera, the giant flash, or the fact that they'd arbitrarily changed the speed limit from 60 to 50 three years prior. Maybe they're just plain effective on that type of person.