Outdoor advertising is now recognised throughout the world as a real selling force. It is also regarded as the most economical form of effective publicity, and these two most important features account for its increasing popularity amongst advertisers.

In choosing an advertising medium, circulation is usually the first consideration. In this respect the outdoor advertisement is unique, in that its circulation is limited only by the number of people who pass its location, and that it is on duty telling its message twenty-four hours a day.

The dimensions of the usual outdoor advertisement, and the fact that it is in colours, assure it of public attention. We may be so occupied with more immediate things that we may not consciously be aware of the influence that the outdoor advertisement is exerting upon us, but consciously, or unconsciously, its constant repetition, day after day, impresses its message upon our minds.