Safety Analysis Based on Systems Theory Applied to an Unmanned Protective Vehicle

Abstract

The project “Automated Unmanned Protective Vehicle for Highway Hard Shoulder Road Works” (aFAS) aims at developing an unmanned protective vehicle to reduce the risk of injuries due to crashes for road workers on German highways. The application of the unmanned protective vehicle has a limited or reduced number of operational situations compared to other use casesand shall show the development and validation of a highly automated vehicle system. To ensure functional safety during operation in public traffic, the system is developed following the ISO 26262 standard. After defining the functional range in the item definition, a hazard analysis and risk assessment has to be conducted. The ISO 26262 standard gives hints on how to process this step and demands a systematic way to identify system hazards. Best practice standards provide systematic ways for hazard analysis, but lack applicability for automated vehicles due to high variety and number of different driving situations, which have to be controlled by the automation system, even with a reduced functional range as met in the project aFAS. Humanmachine-interaction is changing towards less interaction but more important influence, as the driver must select the right operating mode and depending on the level of automation act as a fallback layer. This contribution applies a new method based on systems theory, System-Theoretic Process Analysis (STPA), to the unmanned protective vehicle concept. A crucial topic of this process is to generate a proper control structure for the system and investigate it regarding all (representative) operational situations. We will show our experiences with STPA for the unmanned protective vehicle and summarize questions to the application on automated vehicles.