The paper describes and reports the results of a project that has involved Project Automation S.p.A. and the Italian highway company Società Autostrade S.p.A. The main aim of the project is to deliver a monitoring and control system to support traffic operators of Italian highways in their working activities. The main functionalities of the delivered system are: automatic detection of anomalous traffic patterns, alarm filtering according to peculiarities of the monitored highway section, atomic alarm correlation, and automatic control of traffic anomalies. In particular, the paper gives a general introduction to the System for Automatic MOnitoring of Traffic (SAMOT), its aims, design approach and general architecture. Moreover, more details will be given on the Alarm Correlation Module (MCA), a knowledge–based solution based on Modal Logic approach to the atomic alarm correlation and filtering. Finally, we will show three significant installations of the SAMOT system that are currently working to support traffic operators of some of the most important and traffic congested Italian highways.