Identifying Causes of an Accident in STPA Using the Scenario Table

Hyunsoo Yang, Gihwon Kwon

http://doi.org/10.5626/JOK.2019.46.8.787

In recent years, the complexity of safety-critical systems has increased, along with the importance of the software. The software, which has become the control center of the safety system, generates control actions to control the system and then repeats the interaction of controls that re-enters the feedback generated. STPA (System Theoretic Process Analysis) is one of the hazard analysis techniques, and it analyzes the system from the perspective of the interaction of control then uses accident scenarios to identify and analyze the cause of unsafe control actions to derive safe requirements. In order to minimize omissions in the identification stage of STPA accident scenarios associated with safety requirements, in this paper we describe how to incorporate commonalities and complement vulnerabilities in the approaches described in previous studies. To do this, we propose the detailed procedure for identifying accident scenarios and the scenario table to assist them. The ultimately proposed scenario table is identified by applying it to the hazard analysis of the railway diorama system.