transforming perth

Much attention has been given to the idea of the polycentric city as a model to retrofit low density cities and provide an alternative to urban sprawl. Whilst the nodes of this model can attract concentrated forms of urban development there is also the potential for land along the links between the nodes to provide increased intensity of residents and jobs. What are the constraints to increasing density in these locations in Perth? And what are the implications of this in terms of built form and yield?