Silent cop

A silent cop, also referred to as a "sleeping policeman" or a "traffic dome", is a traffic management device formerly widely used in Australia. It consisted of a metal or concrete dome, about 400 mm (16 in) wide and about 125 mm (5 in) tall, embedded in the road surface. They were usually painted yellow and often decorated with retro-reflective glass beads or "cats eyes". The name has its origins from the Northern Beaches area of Sydney and was derived from the early days of motoring when policemen would be deployed at busy street corners to direct traffic, before traffic signals became widespread.