This paper presents a model-based safety architecture framework (MBSAF) for capturing and sharing architectural knowledge of safety cases of safetycritical systems of systems (SoS). Whilst architecture frameworks in the systems engineering domain consider safety often as dependent attribute, this study focusses specifically on sharing architectural knowledge of safety cases between stakeholders and managing safety in systems development. For this purpose, we adapt the A3 architecture overview (A3AO) tool. The application is shown though the case study of Dutch high speed train lines and shows how to derive requirements from various stakeholders by carrying out iterative validations of the A3AOs. The implemented technique consists of systems modeling language-based (SysML) diagrams. Outcomes of the assessment lead to guidelines for two A3AOs. This results in increasing and effective interaction between stakeholders, more overview for managing safety complexity, more insight into finding required safety information, and therefore; an increasing efficiency in safety engineering