The recent trend in modern systems development can be characterized by the increasing complexity in terms of both the functionality and HW/SW scale that seems to be accelerated by the growing user requirements and the rapid advancement of technology. Among the issues of complexity, the one related to systems safety has attracted great deal of attention lately in the development of the products ranging from mass-transportation systems to defence weapon systems. As such, the incorporation of safety requirements in systems development is becoming more important. Note, however, that since such safety-critical systems are usually complex to develop, a lot of organizations and thus, engineers should participate in the development. In general, there seems to be a variety of differences in both the breadth and depth of the technical background they own. To address the problems, at first this paper presents an effective design process for safety-critical systems, which is intended to meet both the systems design and safety requirements. The result is then advanced to obtain the models utilizing the systems modeling language (SysML) that is a de facto industry standard. The use of SysML can facilitate the construction of the integrated process and also foster active communication among many participants of diverse technical backgrounds. As a case study, the model-based development of high-speed trains is discussed.