"Among the critical areas of software development are Requirements Engineering (RE) and Systems Architecting (SA). There is a high degree of interaction between these two processes. While these processes have been researched in terms supporting technology, there is a distinct lack of empirical understanding regarding the scientific properties of the interaction between RE and SA. Without such empirical understanding, clearly, technical-solution proposals are less likely to be effective in practice. Thus, this proposal seeks to investigate: (1) the impact of an existing system’s architecture on the risks associated with new RE decisions; (2) the role of simulation in the engineering of the requirements of complex systems; and (3) the guidelines that can be used to support the extraction of generalisable requirements and architectural patterns from a prototypical project’s information base for use in developing production systems. These are novel objectives. The significance of the first two objectives is that they would give transparency to the analysts and stakeholders, during requirements change, as to the risks involved in changing and implementing new requirements. Assessment of such risks would be invaluable for negotiation with customers and in system design and technology development. The significance of the third objective is that the cycle-time, effort, and hence cost, for transitioning projects from prototype to production stages could reduce considerably because of the use of established guidelines. This is of strategic importance as we transition more and more “green” prototype systems into production systems. The research approach to be used will entail conducting case studies of a significant prototype automated train project (RailCab). The application domain is thus “mechatronics” (i.e., mechanical engineering, electronics, and software engineering), making this investigation inter-disciplinary."