We have ‘speed check’ signs that light a display with your speed on it if you’re over the limit and the words ‘Check your speed’ (don’t know if you have them too, but we have a lot).
Point is, while it’s taking its data from a sensor concealed (or at least not made obvious) from before you see the sign, and as such actually is your speed, I’ve had a least one conversion where the driver thought it was a general warning, and the back of the sign was taking the speed of the car ahead. (No visible sensor, so must be behind the sign).
Anecdotes are only worth what they weigh, but this person wasn’t a dumb cookie, and even they thought that.
So yes, more ‘Yes, we mean you!’ in the signs. 
