This paper investigates the state-of-the-art with respect to simulation-based planning support systems in order to draw a set of requirements and best practices for an urban planning and design framework that enables multiple stakeholders with differing perspectives to systematically explore design options, leveraging the latest analysis and simulation techniques. From these requirements and best practices, the foundations and structure of such an urban planning and design framework are developed. A number of technological and methodological challenges are identified for future investigation.