The understanding and conceptualization of cities and its constituent systems such as transportation and healthcare as open and complex is shifting the debates around the technical and communicative rationales of planning. Viewing cities in a holistic manner presents methodological challenges, where our understanding of complexity is applied in a tangible fashion to planning processes. Bridging the two rationales in the tools and methodologies of planning is necessary for the emergence of a 'non-linear rationality' of planning, one that accounts for and is premised upon complexity. Simulations representing complex systems provide evidence and support for planning, and have the potential to serve as an interface between the more abstract and political decision making and the material city systems.

Moving beyond current planning methods, this thesis explores the role of simulations in planning. Recognizing the need for holistic representations, the thesis integrates multiple disparate simulations into a holistic whole achieving complex representations of systems. These representations are then applied and studied in an interactive environment to address planning problems in different contexts. The thesis contributes an approach towards the development of complex representations of systems; improvements on participatory methods to integrate computational simulations; a nuanced understanding of the relative value of simulation constructs; technologies and frameworks that facilitate the easy development of integrated simulations that can support participatory planning processes.

The thesis develops contributions through experiments which involved problems and stakeholders from real world systems. The approach towards development of integrated simulations is realized in an open source framework. The framework creates computationally efficient, scalable and interactive simulations of complex systems, which used in a participatory manner delivers tangible plans and designs.