This paper examines the development of urban transport political agendas in three Nordic capital cities, Helsinki, Oslo, and Stockholm, that strive towards urban sustainability. Utilising the Multiple Streams framework as a basis for analysis, an overview of local problems, policy solutions, and politics that have characterised transport systems and the related policy development processes over time is constructed. The attention is then drawn towards the points in time where the streams connect, and policy windows occur, to detect formative changes and their enablers towards sustainability. The data consists of 18 semi‐structured expert interviews, conducted amongst municipal policymakers and planners. The results reveal several policy windows that have transformed the local transport systems towards sustainability and an increasingly people‐oriented approach. The relevance of global climate change awareness, international planning trends for liveability and cycling, public pressure, individual political decisions, and establishment of modal hierarchy is evident across the case cities, while car traffic regulation is politically challenging and addressed through very different means at very different times. The findings of this paper outline diverse ways for advancing sustainability in local policy development but also detect methods for politically halting the process.