Walkability Indices-The State of the Art and Future Directions: A Systematic Review

This systematic review aims to illustrate the state of the art of walkability indices and future research directions. A comprehensive search in the general Google database and Google Scholar identified a total of 45 records published between 2005 and 2023. Using a selection process based on the PRISMA model, 32 records were identified as meeting the inclusion criteria. These are organized incrementally, highlighting their novelty relative to preceding studies, and divided into sectors of prevalent application. The 5Ds theory provides a first contribution by identifying walkability metrics based on proximity to amenities, land use diversity, and density. Recent advancements, leveraging GIS systems and open data, have expanded such metrics to include green spaces, footpath design, and noise pollution. However, these developments remain largely tied to the catchment area logic and offer coarse descriptions of the built environment's morphological structure, often lacking justification for metric selection and weighting. To address these shortcomings, future research should use more detailed descriptions of urban form, balance metric comprehensiveness with data availability, employ robust methods for metric selection, and explore alternative weighting techniques based on cognitive and emotional responses to urban settings. These efforts are crucial for advancing the understanding and measurement of walkability in the context of the compact city and place-making paradigms.