A major challenge for all cities is to reconcile growth with cultural, social and environmental considerations, along with connecting urban design with opportunities for health and wellbeing. Planning Support Systems (PSSs) can facilitate future planning and foster collaboration between researchers and urban planners in promoting healthy built environments. The Walkability PSS was developed specially for that purpose. This chapter presents an evaluation of the Walkability PSS, a PSS for building planning scenarios and assessing their impacts on walking behaviours. The evaluation was conducted in collaboration with a group of local urban planners. The study results show that the Walkability PSS could support planners in several situations including testing and comparing planning scenarios for greenfield and brownfield areas, conducting consultation and/or workshops with various stakeholders and making decisions about the provision of new infrastructure.