Databases provide information on viewership for messages. In some embodiments the database can describe the numbers and/or type of pedestrians who can watch public displays at different locations and times. The displays can be outdoors and/or vehicle mounted. The database can be updated by information...http://www.google.de/patents/US20020111146?utm_source=gb-gplus-sharePatent US20020111146 - Apparatuses, methods, and computer programs for displaying information on signs
