It seems certain that achieving the scale of change in the production of the built environment necessary to save the world from the threat of rapid global warming, and consequent climate shocks, will require profound institutional change over a range of policy domains. Such change must encompass more than organizational structures, and includes a change in assumptive worlds and embedded funding programmes. The institutional momentum behind existing policies is strong. Policies are produced in a manner that can be described as 'path dependent'. In this paper, we argue for a multivalent conception of path dependence containing three interwoven strands: technical, institutional, and discursive path dependence. The empirical focus of this paper is the discursive aspect of path dependence in transport planning with reference to research in Melbourne, Australia.