An STPA-Based Analysis of Automated Driving Systems Fleet Maintenance Activities

Automated Driving Systems (ADS) are complex systems composed of several sub-systems whose interaction may lead to emerging properties and unintended behaviors. The expected deployment of vehicles equipped with SAE Level 4 (L4) ADS for Mobility as a Service (MaaS) in the medium future requires a thorough operational safety analysis. The application of risk assessment methods to ADS technologies has been mostly limited to hazards originating from hardware or software malfunctions. Nevertheless, risk analyses of complex systems must also include organizational safety and human-related issues, as they are crucial in ensuring ADS operational safety and gaining the public's trust [1], [2]. In particular, MaaS operations add safety aspects that require appropriate methodologies to be addressed, such as passengers' behavior, fleet operators, and communication between fleet operators, ADS developers, and ADS vehicle manufacturers. Identifying and analyzing sub-systems' and emergent failures is crucial for preventing and mitigating risks during operation. This work presents the application of a system-level System-Theoretic Process Analysis (STPA) to L4 ADS fleets employed for MaaS. This method is employed to identify key actions and responsibilities of multiple agents vital in supporting the safe operation of the ADS vehicles. This work studies the interaction between distinct fleet operator agents dedicated to fleet monitoring and vehicle maintenance tasks. The present analysis focuses on identifying safety hazards that may occur during vehicle inspection and maintenance activities. Identifying key roles and responsibilities of key actors within the L4 ADS fleet ecosystem may lead to more robust safety barriers, including procedure development and crew training.