Policy decision-making and implementation face increasing complexity, characterised by wicked problems and persistent resource limitations (Mueller, 2020). Policymaking has transitioned from linear, causality-driven models to more adaptive and interactive methodologies (Peters, 2018). Human-centred design (HCD) can augment policy legitimacy by prioritising citizens' experiences and evaluating effects on broader stakeholders. Personas, an HCD tool representing fictional user profiles (Miaskiewicz & Kozar, 2011), provide potential value, although their primary application is in commercial design. However, policymakers exercise caution, as potential limitations in accessibility, usability, and contextual relevance may hinder adoption. Without critical adaptation, transferring design tools into policy contexts risks weakening both design integrity and policy legitimacy (Peters, 2018), leaving the integration of personas in policymaking underexplored.

This research investigates how personas can be effectively integrated into policymaking processes. The project has two main components guided by two research questions:

• Qualitative: How can personas be effectively integrated into policymaking processes?
• Quantitative: How does incorporating persona‑level data influence the behaviour and outcomes of a complex system compared with using aggregate data?

The research employs an interdisciplinary methodology, incorporating human factors, systems thinking, system dynamics, and policymaking. Developed in partnership with the Department for Transport (DfT), the PhD focuses on the UK transport context. The findings address a knowledge gap concerning the application of personas in design, specifically their capacity to enhance policymaking processes. This research further substantiates the argument for HCD in policymaking by illustrating how personas can assist policymakers in effectively addressing the needs of diverse population groups during the design and implementation of policy.