Learning from Incidents in Socio-Technical Systems: A Systems-Theoretic Analysis in the Railway Sector

Post mortem incident investigations are vital to prevent the occurrence of similar events and improve system safety. The increasing interactions of technical, human and organizational elements in modern systems pose new challenges for safety management, demanding approaches capable of complementing techno-centric investigations with social-oriented analyses. Hence, traditional risk analysis methods rooted in event-chain reactions and looking for individual points of failure are increasingly inadequate to deal with system-wide investigations. They normally focus on an oversimplified analysis of how work was expected to be conducted, rather than exploring what exactly occurred among the involved agents. Therefore, a detailed analysis of incidents beyond the immediate failures extending towards socio-technical threats is necessary. This study adopts the system-theoretic accident model and process (STAMP) and its nested accident analysis technique, i.e., causal analysis based on systems theory (CAST), to propose a causal incident analysis in the railway industry. The study proposes a hierarchical safety control structure, along with system-level safety constraints, and detailed investigations of the system's components with the purpose of identifying physical and organizational safety requirements and safety recommendations. The analysis is contextualized in the demonstrative use of a railway case. In particular, the analysis is instantiated for a 2011 incident in the United Kingdom (UK) railway system. Hence, the CAST technique requires information regarding incidents, facts and processes. Therefore, the case study under analysis provided the information to analyze the accidents based on system theory, in which the results of the analysis prove the benefits of a CAST application to highlight criticalities at both element- and system-level, spanning from component failure to organizational and maintenance planning, enhancing safety performance in normal work practices.