Infrastructure projects undergo multiple changes throughout their lifecycle, adapting to new mobilities, technologies and environments. We build on the System of Systems (SoS) theoretical concept to understand the implications of such infrastructure transformations, specifically when projects move from a single purpose to hosting multiple functions. Using multiple case studies in Europe, we investigate which functions will likely be added to the original infrastructure and the rationale for adding these functions. Therefore, we expand upon the theoretical concepts of circularity, resilience, and social sustainability, wherein multifunctional infrastructure adapts, renews, and complements existing infrastructure.