Sustainability policy making is hampered by a tendency towards sector-based, short-term and often techno-fix perspectives. This paper describes a novel policy development and assessment framework - Integrated Sustainability Assessment (ISA) - that may help address problems of unsustainability in a more integrated and strategic manner. ISA involves two primary methods: transition analysis and stakeholder engagement. The ISA case study on sustainable passenger mobility suggests ISA is well equipped to produce a holistic analysis of mobility systems, illustrate radical alternatives to the status quo and foster social learning. Further research should explore its potential to induce long-term behavioural or institutional change.