A proposal of hazard analysis method using structured system theoretical process analysis

System Theoretic Process Analysis (STPA) is a method for analyzing hazards caused by interactions between components of an industrial product. STPA is applied in the upper stream stages of industrial product development, STPA detects hazards while referring to the whole configuration of the industrial product. Therefore, STPA generally does not deal with detailed information about the industrial product. Since the information on the industrial product is insufficient, it is difficult to clarify the factors of hazards, the occurrence order of factors, and the conditions that occur the hazard by STPA. Therefore, the following methods were added to the conventional STPA; the method of describing the components of industrial products in hierarchical detail, the method of clearly defining the behaviour of each component, and the method of tracking the structured CSD to clarify the causes of the hazard. By adding those methods, it became possible to conduct a hazard analysis of the industrial product in detail. As a result of applying the proposed method to the existing railroad crossing control system, it was confirmed that the proposed method could detect more factors of hazards and create adequate scenarios from the occurrence of hazard causes to the occurrence of the hazard.