An index of accessibility-based vulnerability is created based on a definition of transport-user vulnerability regarding transport accessibility created for the EMPOWER project, in order to assess the project’s key performance indicator of the inclusion of vulnerable people in the project’s scheme. The objective of the index is to account for various individual vulnerability aspects, but also for the ‘multi-dimensionality’ of vulnerability, i.e. individuals may be vulnerable because of one specific aspect (e.g., disability), or they may be vulnerable because of multiple aspects which, if assessed in isolation, wouldn’t classify the individual as vulnerable. Users of the project scheme in the Dutch city of Enschede are surveyed on, inter alia, their vulnerability based on this definition, according to their income, mobility budget, physical mobility, age, gender, living situation, nation of birth, and education. According to individual questions, 1% to 54% (single parents and females, respectively) of respondents have some level of vulnerability. According to the index, 23–36% of respondents can be considered to be vulnerable. Suitably modified for local conditions, the index is relevant to cities, especially quickly developing cities where congestion reduction is or has been a priority, insofar as it offers a way of measuring and monitoring the vulnerability of the users of their transport system. Finally, steps to adapt the index to other settings (cities or countries) are discussed.