Systems Approach to Creating Test Scenarios for Automated Driving Systems

Increased safety has been advocated as one of the major benefits of the introduction of Automated Driving Systems (ADSs). Incorporation of ADSs in vehicles means that associated software has safety critical application, thus requiring exhaustive testing. To prove ADSs are safer than human drivers, some work has suggested that they will need to be driven for over 11 billion miles. The number of test miles driven is not, by itself, a meaningful metric for judging the safety of ADSs. Rather, the types of scenarios encountered by the ADSs during testing are critically important. With a Hazard Based Testing approach, this paper proposes that the extent to which testing miles are 'smart miles' that reflect hazard-based scenarios relevant to the way in which an ADS fails or handles hazards is a fundamental, if not pivotal, consideration for safety-assurance of ADSs. Using Systems Theoretic Process Analysis (STPA) method as a foundation, an extension to the STPA method has been developed to identify test scenarios. The approach has been applied to a real-world case study of a SAE Level 4 Low-Speed Automated Driving system (a.k.a. a shuttle). This paper, discusses the STPA analysis and a newly-developed test scenarios creation method derived from STPA.