The UK Climate Change Act 2008 commits to a reduction of 80% in national GHG emissions by 2050 compared to 1990 levels. This article explores what happens next where these top-level aspirations are expected to be turned into radical action. It does so through examination of the transport sector, which is a highly complex, fragmented, and multi-level delivery environment. The research draws on cases studies of four major cities with different governance structures within the two distinct, yet connected, national contexts of England and Scotland. It integrates a range of theoretical legacies, namely ‘muddling through’, multi-level governance, and positional analysis, to look across governmental layers and out to non-governmental actors at all levels. Underneath the 80% target, the framework for action remains unclear. Lower-tiered authorities report difficulties in acting in a more comprehensive or rapid manner than upper tiers of government, largely because of the potential costs involved and a significant resource dependency on national governments. Ambition is also tempered by conflicts with economic growth objectives and the difficulties in aligning the objectives of the myriad of public and private organizations that need to take action.