Nonlinear degradation of system configuration during the development of an accident

This paper utilises a methodology named “Risk SituatiOn Awareness Provision” (RiskSOAP). RiskSOAP expresses the capability of a system to meet its safety objectives by controlling its processes and communicating threats and vulnerabilities to increase the situation awareness of its end-users and support their decision-making. In reality safety-related system features might be partially available or unavailable due to design incompleteness or malfunctions. Therefore, respectively, the availability and capability of RiskSOAP mechanisms might fluctuate over time. To examine whether changes in RiskSOAP values correspond to a system degradation, we used the results of a previous study that applied the RiskSOAP methodology to the Überlingen mid-air collision accident. Complementary to the previous application where the RiskSOAP was calculated for four milestones of the specific event, in this study we divided the accident further into seventeen time-points and we calculated the RiskSOAP indicator per time-point. The results confirmed that the degradation of the RiskSOAP capability coincided with the milestones that were closer to the mid-air collision, while the plotting of the RiskSOAP indicator against time showed its nonlinear fluctuation alongside the accident development.