Speed trap signs?

Hit the books and figure these out ahead of time, just in case. Don't want to find yourself in a panic when you see one of these bad boys forcefully inserted into your favourite motorway:

I don't know about you, but they make me anxious. Be the first to tell me what the speeds are and I'll buy you a pint for the favour (I'll probably just be walking or hitchhiking in the meantime). That's a serious offer, too.