In this paper FMECA (Failure Mode, Effects and Criticality Analysis) technique was applied on an complex electromechanical device. In particular, the device under examination is an automatic toll collection system. By using the field data collected in functioning condition it has been possible to evaluate the criticality of each element of the system under study. Finally, an economic analysis was applied using the FMECA technique thus to obtain a complete acknowledgement of the system employed.