From Advertising/Design Goodness:
A driver from a distance will see a police car hiding behing a billboard, as the police typically do in Turkey/ thus the driver instinctively slow down or make sure that they are going at the legal speed limit. When they come closer they are able to read the billboard text:
Pay your traffic tickets on time without waiting in line - isbank.com.tr
However just as they pass the billboard they will realize that there really isn’t a police car hiding there. That actually is a full size reproduction of a police car which is a part of the billboard.