STPA-Inspired Safety Analysis of Driver-Vehicle Interaction in Cooperative Driving Automation

Abstract: Autonomous vehicles occupying public roads are becoming a reality, and the addition of cooperative functionality open up new possibilities to ensure safer and more efficient traffic solutions than today’s manual drivers ever could. However, in order to implement these systems, they need to be proven safe. This thesis focuses on cooperative driving and the human-machine interaction of autonomous vehicles in order to provide safety analyses. The research is based on a case study of KTH’s participation in the 2016 GCDC competition for autonomous cooperative vehicles, where their performance in three real-life inspired traffic situations was measured. The functional safety of the necessary added cooperative driving functionality is assessed using the, in the automotive industry relatively new, method of Systems Theoretic Process Analysis (STPA) resulting in a number of system level safety constraints. The analysis concluded a lacking development in HMI-related aspects, and the item under analysis is enhanced in all driver-vehicle interaction aspects. This development introduces a direction for visual aspects and two new driver-centric hazards of mode confusion and unfair transitions, risking the vehicle being left uncontrolled or thought to be controlled by both autonomous systems and the driver simultaneously. A suggested input sequence to ensure a safe transition between autonomous and manual states is also included. The enhanced item, resulting in new possibilities of driver-vehicle interaction, was then analysed; comparing STPA with a new method introduced for safe mode switching in autonomous vehicles to identify HMIrelated hazards. The results concluded accidental input or faulty inputs from the driver as the main threat towards mode confusion. These would often be caused by malfunctioning controls for mode transition or faulty indications on the dashboard.