Like others, it's the covert nature of these vans/cars/guns etc that annoys me. They've stopped calling them speed cameras and started calling them safety cameras, well as others have said, if it's about safety why hide?
In my eyes it's all about reminding me of what speed I should be doing, seeing a police car, or one of those flashing 30mph signs does work for me.
And, as others have said if it's about safety why shouldn't motorists warn other drivers? Surely it's all about getting the cars to slow down through the "accident blackspot" or whatever the criteria is behind placing a camera somwhere.
A little food for thought, a camera van is hidden; a car is doing 40mph in a 30mph zone, he goes through the trap and gets a fine, keeps going at 40 because he's not seen the van and then hits a child 5 metres down the road from the van, in this case the poilice make some money and the child dies. Senario 2: I warn the driver of the car, he slows down to 30, passes the van without setting off the cash machine and manages to swerve to avoid the child because he's travelling at the correct speed.....so.....money to the police or a child's life.....?
Saying all that, if none of us sped, we wouldn't have anything to worry about!