A unified safety framework for automated vehicle development: integrating ISO 26262, SOTIF, and UL 4600

• Introduces a unified framework integrating ISO 26262, SOTIF, and UL 4600. • Combines STPA and HARA into a coherent hazard and ASIL mapping workflow. • Aligns SOTIF functional insufficiency hazards with ISO 26262 safety goals. • Applies the framework to Level 2 Adaptive Cruise Control with Lane Centring. • Supports structured traceability and cross-standard safety documentation. The safe deployment of Automated Vehicles (AVs) requires the coordinated application of multiple safety standards, each addressing distinct aspects of system performance and risk. This paper introduces a unified safety framework that integrates ISO 26262, ISO 21448 (SOTIF), and UL 4600 to support comprehensive safety assurance across the AV development lifecycle. The study begins by outlining a structured methodology for identifying, analysing, and synthesising relevant standards and academic literature. A key contribution of this work is the integration of System-Theoretic Process Analysis (STPA) with the Hazard Analysis and Risk Assessment (HARA) process, enabling system-level performance-related hazards identified through STPA to be systematically classified and assigned Automotive Safety Integrity Level (ASIL) levels via HARA. This combined workflow provides a coherent mechanism for mapping hazards, safety goals, and functional requirements across the three standards. A harmonised safety framework is then developed, aligning the complementary strengths of each standard within the concept and early design phases. The framework is validated through a detailed case study of Adaptive Cruise Control with Lane Centring, a representative Level 2 automation feature. The case demonstrates how the unified framework can enhance traceability, reduce redundancy, and support consistent cross-standard compliance. Broader challenges, including evolving AV software behaviours and the applicability of UL 4600 to lower automation levels are also identified. This research offers a structured, standards-based methodology that strengthens practical safety assurance and establishes a foundation for scalable, transparent, and unified AV safety practices.