<p>Modern vehicles operate as Systems of Systems, with tightly coupled interactions with many subsystems. As a result, traditional item-level safety analysis based on ISO 26,262 often leads to redundant or omitted hazards, limiting the ability to assure comprehensive vehicle-level functional safety. This study proposes the Vehicle-level Integrated Functional Safety Framework (VISEF) to overcome these limitations by enabling holistic safety analysis across subsystems. VISEF consists of three key stages. First, a conventional item-level hazard identification and ASIL assignment process is conducted. Second, hazard integration is performed using functional, operational, and scenario-based similarity measures to identify and consolidate redundant hazards, followed by ASIL reallocation. Third, safety path inspection is applied by generalizing control flows between ECUs into structured input-processing-output streams. To validate the framework, a dual-pronged evaluation approach was employed. A nonlinear probabilistic saturation model was used to compare the system-level safety assurance probability before and after applying VISEF. Additionally, VISEF was applied to an actual commercial xEV truck/bus project. This study provides both experimental and empirical evidence that integrated vehicle-level hazard management contributes to system-level safety. VISEF offers a structured, scalable methodology for extending ISO 26,262, and establishes a foundation for future standardization in vehicle-level functional safety engineering.</p>