A methodology for the analysis of SPAD

This paper describes a methodology for investigating the incidents where a train passes a signal displaying a danger aspect, without authorisation (SPAD). The methodology combines the analysis of historical databases concerning the SPAD events with the investigation on the field. The investigation considers all the components that support the train driver in performing his activity. The application of the methodology has shown that a strong involvement of the stakeholders is very important to understand the real operative procedures and the way the supporting components are used by the train drivers and by the other relevant users. Operative procedures and role of components are sometimes quite different from those hypothesized by the system designers. The paper describes the analysis of a real incident to illustrate the application of the methodology, and to show the importance of understanding the real operative procedures adopted by the train drivers