The need to move away from fossil fuel powered transport is now well established, and cities are often seen as the places par excellence where sociotechnical transitions towards sustainable, low-energy mobility are in the making. Yet, exactly why some cities are more successful in moving towards lower energy consumption than others remains only partly understood. This presentation will argue that this is partly the consequences of academic research on ‘niche innovations’ in urban transport and other domains are more focused on internal dynamics of individual niche innovations rather than their entanglements with each other and the wider political, institutional, economic, social and physical contexts in which they emerge. It will therefore develop a relational approach to the emergence of niche innovations in urban transport that is inspired by the philosophy of Alfred N Whitehead and various recent reinterpretations of his original writings. The approach will be used to analyse recent developments in low-energy mobility in three contrasting case study areas in the UK – Merseyside, Brighton and Oxford.