Mobility as a Service (MaaS) is the use of a “digital interface to source and manage the provision of transport related services” which meet peoples mobility requirements. The implementation of a MaaS based transport system is dependent on a city possessing a number of characteristics. Before planning for MaaS it is important for decision makers to understand how close a city is to fulfilling these characteristics. Therefore, the aim of this study is to develop the ‘MaaS Maturity Index’. This measures a cit’s readiness for MaaS implementation based on characteristics across five dimensions: 1. Transport operators data sharing and openness, 2. Citizen familiarity and willingness, 3. Policy, regulation and legislation, 4. ICT infrastructure, and 5. Transport services and infrastructure. The index has been applied to two metropolitan areas in the UK; London and the West Midlands. The results indicate that, as expected, London is slightly more ready for MaaS than the West Midlands, but that both cities have lots of room for improvement.