Unravelling Safety-Critical Situations in Remote Operation Mode for Automated Trains - A Systematic Approach with STPA

Automation is increasingly becoming an integral part of mainline rail operations. However, there are still significant challenges to be overcome on the way to fully automated mainline operations (grade of automation 4, GoA4). Ensuring safety in all GoA4 operational scenarios is paramount. By employing System-Theoretic Process Analysis (STPA), this paper aims to systematically analyse the control structures and processes of remote operation mode in fully automated railway operations to derive potential safety risks. By identifying and addressing safety-critical situations, railway operators can enhance the reliability, efficiency, and safety of fully automated railway systems by mitigating the reasons for safety-critical situations before the system migration. In fully automated railway operations, where various subsystems and components interact dynamically, understanding these systemic relationships is crucial for identifying safety-critical situations. STPA considers the interactions and dependencies between the system components within the system architecture and allows to identify hazards from the point of operational view (systemic view). In this paper, 11 safety-critical situations occurring during remote operation mode of automated trains could be identified using STPA. Additionally to the identified safety-critical situations, possible architectural and operational safety measures are presented.