The "sleeping policeman" is a somewhat quaint name for the traffic calming device more commonly referred to as the speed bump. Intended to slow vehicles down by presenting a small obstacle, the sleeping policeman is usually a rounded, "half sausage", mound of tarmac or concrete, several inches high and running across the road, perpendicular to the flow of traffic.

Despite advanced warning of their placement in the road, such as a distinctive paint pattern or warning sign, "sleeping policeman" usually end up scarred by the impact of oil sumps of cars with inattentive drivers. "Wear your medals with pride, boys!"

Why this particular piece of "street furniture", (Don't you just hate that phrase?!), is called a "sleeping policeman" is anyone's guess but it's probably something to do with the fact that it's a passive, ("sleeping"?), device that causes traffic to slow down, much like the presence of a real policeman would, (in theory at least).