Accessibility securing capabilities: an international Delphi study examining experts' priorities

Accessibility has long been recognised as a key concept linking transport, land use, and social inclusion. Yet, despite its widespread use, fundamental questions remain unresolved about what accessibility represents and how it should be conceptualised. A variety of definitions and measurement approaches reflect different assumptions about what counts as relevant opportunities, acceptable travel effort, and legitimate beneficiaries, revealing the deeply normative and subjective nature of accessibility indicators. This paper addresses these conceptual tensions through a ranking Delphi study with an international panel of transport scholars and practitioners. Drawing on the Capability Approach and understanding accessibility as the potential to realise valued capabilities, the study examined how participants prioritise the capabilities that accessibility should secure, and the factors that enable or constrain them, in general terms and across specific contextual scenarios. Results show broad alignment on the importance of capabilities related to basic mobility and physical integrity, but persistent divergence on whether accessibility should also secure capabilities linked to agency and individual choice. Priorities also shifted with context: in a leisure scenario, for example, capabilities related to emotional wellbeing gained priority over those related to physical health and integrity. Participants largely agreed on the salience of tangible conversion factors—such as affordability, infrastructure quality, and personal ability—but consensus weakened when multiple, interacting factors were considered. Overall, the findings illustrate the value-laden nature of accessibility and point to the need for explicit reflection on its normative foundations in both research and policy. In this regard, the Capability Approach offers a valuable foundation for researchers and practitioners to engage more transparently with the normative choices that shape how accessibility is defined, measured, and pursued.