To address Sydney’s demand for housing, new suburbs are being masterplanned and created on the sites of paddocks and rural residential areas, known as “greenfield release area” development. These areas are generally located in the city fringe and can be isolated and disconnected from the existing urban fabric. The masterplans for these new subdivisions often provide for them to have their own facilities and services, but timing of the delivery of this infrastructure is not known at the outset and may be many years after residents have moved in. There is a growing reliance on developers, rather than Local or State government, to provide this infrastructure. This research uses a Systems Thinking approach to identify the infrastructure that should be provided in new release areas to support the development of connected and sustainable communities. It is particularly focused on the physical infra-structure that facilitates social life through activity and interaction. Systems Thinking offers a means of thinking about infrastructure needs and priorities as a system, leading to decision support models that are robust and can account for the flow on effects of decisions. This research develops a unique combination of Soft Systems Methodology and System Dynamics to generate a multi-methodological approach that can be used to understand both the technically-centred infrastructure variables and their relationships, and the human-centred decision making process. By combining quantitative and qualitative techniques, new insights and tools for managing infrastructure planning issues can be obtained, which is particularly important given that infrastructure delivery is often limited by funding and land availability and will have long lasting implications for the formation of connected and sustainable communities.