The chapter builds on open-source approaches to develop an early version of a planning support system (PSS) for scenario planning underpinned by cumulative accessibility modelling, Transport Accessibility PSS (TAPSS). In this chapter, we discuss the potential benefits of including rapid route-option testing and dynamic visual feedback on strategic goals through streamlined modifications to the timetable and route characteristics of existing and hypothetical transport networks. A case study of a potential mega-region in New South Wales, Australia, is investigated in the context of these PSS tools. The focus is on one type of access opportunity, employment, and evaluating how successful this metric performs over a combination of speed and connectivity options across the region. These are based on current and historic strategies. With the availability of similar data, the process is adaptable to other cities worldwide. It assists with an essential task for planners and decision-makers, and provides a process and medium by which to communicate and collaborate on similar tasks with other practitioners and non-expert users.