Drawing on and developing literatures on automobilities, vertical urbanisms and the use of storylines to understand mega transport projects, we imagine infrastructure as a shifting assemblage of actors, storylines and material objects and practices. In the case of motorway building, this requires an understanding of how competing storylines about how both the infrastructure itself and the city it is located in are mobilised and politicised across diverse local geographies and multiple scales as the process proceeds. Our case study focuses on WestConnex, a 33 km motorway being built in Sydney, Australia. Similar to other major transport infrastructure projects, WestConnex morphed over time, growing in ambition, budget, complexity, debate and by enrolling new actors.