In the field of Public Transport, the safety analyzes are carried out in accordance with the requirements defined in CELENEC EN 50126-1, following the guidelines expressed in CELENEC CLC / TR 50126-2.
In this context, the principle of continuous risk management is applied, so that the safety analysis, primarily the risk analysis, are repeated in various phases of the system lifecycle.
During the design phase of the system the so-called "preliminary risk analysis" is performed. It consists of a first identification of sources of dangerous situations that can potentially affect the performance RAMS (reliability, availability, maintainability and safety) system, including possible interactions with other systems and interactions with people.
The preliminary identification of dangerous situations is done by making use, if any, of checklists documented in the literature, historical data, and, in more complex cases, by following the structured approach documented in CLC / TR 50126-2 based on grouping hazard in independent sets and with common characteristics, called hazard cluster, and classifying the hazard in three different hierarchical levels: "top-level hazard", "interface hazard" and "hazard at system boundaries".
In this phase the first version of the "hazard-log" (log of dangerous situations) is drawn up.