Proceedings of the 33rd European Safety and Reliability Conference (ESREL 2023) Edited by Mário P. Brito, Terje Aven, Piero Baraldi, Marko Čepin and Enrico Zio ©2023 ESREL2023 Organizers. Published by Research Publishing, Singapore. doi: 10.3850/978-981-18-8071-1_P326-cd Safety hazard identification of inspection and maintenance operations for Automated Driving Systems in Mobility as a Service Camila Correa-Jullian 1,2 , John McCullough 1 , Marilia Ramos 2 , Ali Mosleh 2 , Jiaqi Ma 2,3 1 Dept. of Mechanical and Aerospace Engineering, University of California, Los Angeles, USA. E-mail: ccorreaj@ucla.edu 2 B. John Garrick Institute for the Risk Sciences, University of California, Los Angeles, USA E-mail: marilia.ramos@ucla.edu , mosleh@ucla.edu 3 Dept. of Civil and Environmental Engineering, University of California, Los Angeles, USA. E-mail: jiaqima@ucla.edu Cooperative decision-making between humans and automated agents operating at various levels of autonomy (LoA) is an increasing trend observed across multiple industries and research areas. Assessing emerging properties and unintended behaviors in complex engineering systems is key to developing policies to prevent and mitigate risks during operation stages. An aspect often overlooked in analyses of autonomous system operation is developing and enforcing adequate inspection and maintenance policies. In this work, the Concurrent Task Analysis (CoTA) method is used to analyze the operation of a Level 4 Automated Driving System (L4 ADS) fleet employed for Mobility as a Service (MaaS). The method is employed to define tasks and responsibilities key to supporting the safe operation of the ADS vehicles based on a functional breakdown of the system, the development of operational scenarios, and the identification of safety hazards. The CoTA describes the interaction between distinct fleet operator agents (e.g., fleet monitoring and vehicle maintenance), identifies critical tasks, and traces cascading and latent failures between them. This paper presents the CoTA of the inspection and maintenance operational phases and discusses the safety implications on the fleet operator’s safety responsibilities to ensure adequate operation of the ADS fleet. Keywords: Concurrent task analysis, automated driving systems, safety assessments, mobility as a service, inspection and maintenance procedures. 1. Introduction Autonomous Driving Systems (ADS) vehicles are poised to transform the transportation landscape in the future. The Society of Automotive Engineers (SAE) establishes six levels of vehicle automation. Level 5 represents a fully self-driving vehicle that operates without human intervention and is unrestricted in its operational range. Level 4 (L4) ADS, on the other hand, can perform all Dynamic Driving Tasks (DDT) within a designated Operational Design Domain (ODD) and may require human input under certain conditions (SAE International, 2021). Vehicles equipped with L4 ADS are becoming commercially available in the context of Mobility as a Service (MaaS). Companies such as Waymo and Cruise are some of the leading companies in the U.S. in terms of developing, testing, and deploying these vehicles. Amid the currently evolving technical, commercial, and regulatory environment, using L4 ADS for MaaS raises questions about how developers and fleet operators may provide adequate safety assurance prior to widespread commercialization and deployment. Recent incident reports collected from testing and small- scale deployment imply that a more focused approach on operational safety is required, for instance, to avoid traffic disruptions, or to determine appropriate incident management procedures (National Highway Traffic Safety Administration, 2022). The latter may become an important element when scaling operations where passengers are on-board a vehicle with no safety driver. In general, efforts in assessing the safety of ADS vehicles have focused either on aspects of functional safety and component-level reliability, 281