With growing urban populations, higher mobility needs, limited available space for transport infrastructure, and the increasing need for more attractive urban areas, these urban areas are faced with a complex dilemma, which gets more challenging by the day. This paper examines the role of flexibility in the relationship between structural spatial development and passenger transport, its economic, environmental, and social perspectives, the long-term impacts of this relationship and the role of this relationship in developing countries. The paper identifies the need for a better understanding of long-term flexibility in development options in order to make better future-proof decisions as a key research avenue, and sets a pathway to achieve this. Main research gaps as identified in the paper include the lack of understanding on the potential for flexibility in optimizing the structural spatial development and passenger transport relationship, the valuation of flexibility, and the application of flexibility approaches in developing countries. This paper emphasizes the importance of acting sooner rather than later, since the future costs of sub-optimal development are rising by the day and the bill is being pushed towards future generations.