Hierarchical Safety Control Structure Diagram

In this approach, a system is viewed as hierarchical structures where each level imposes constraints on the activities of the level beneath them and accidents are viewed as the consequence of inadequate control of safety constraints. Hierarchical safety control structure diagram represents a feedback and control structure of the system. Controls are represented by downwards arrows showing a reference channel with the information necessary to impose safety constraints on the level below. Feedback is represented by upwards arrows that show the measuring channel with feedback returned up the hierarchy on how effectively constraints are being satisfied.

Hierarchical Safety Control Structure Diagrams are usually used as part of System Theoretic Accident Model and Processes (STAMP) (Leveson, 2004). STAMP is a generic approach based on systems theory and particularly suitable to the analysis of complex large scale accidents. The method might be less simple to learn and use than AcciMap.

STAMP has also been used to analyse accidents in various domains, e.g. aviation  (Allison, 2017), patient safety (Leveson, 2016) and marine transportation (Kim et al., 2016).