A system for monitoring a traffic management system, such as an Air Traffic Management (ATM) system, which includes a position retrieval station, operable to retrieve position information for a traffic object, e.g. a radar station devised to collect radar echoes and generate radar image signals. A computer system is connected to the position retrieval station for generating radar trace data from received position information. An operator station is connected to the computer system for processing trace data for presentation. A false position information source is connected to provide artificial information corresponding to a predetermined property of a false traffic object to the computer system. A comparator unit is connected to the operator station for receiving trace data generated from the artificial information, and devised to detect correlation between the generated trace data and the predetermined property of the false traffic object.