Quantifying transitionality for public In-between spaces: an integrated spatial evaluation framework

Public in-between spaces–urban thresholds connecting buildings, streets, and open areas–play a crucial role in mediating movement, legibility, and social experience. However, despite their importance, there remains a lack of quantitative frameworks capable of assessing their transitional quality in an integrated and replicable manner. Existing approaches tend to address spatial configuration, visual perception, or environmental comfort separately, leaving a methodological gap in evaluating these dimensions together. This study introduces a Transitionality Index (TI) that bridges this gap by integrating spatial, perceptual, and environmental indicators into a unified, data-driven evaluation model. The framework combines space syntax metrics (integration, choice, and connectivity) with visibility analysis (VGA), functional diversity, and environmental factors (surface typology, solar shading, and vertical diversity). Indicators are normalized and weighted using Shannon entropy to construct a composite index applicable across urban contexts. Applied to three large public complexes in Istanbul–Zorlu Center, Torun Center, and the Gazhane Museum–the results reveal that functional diversity is the most influential factor shaping transitional spatial quality. The study concludes by demonstrating how the TI model provides an integrative and reproducible framework for evaluating the experiential potential of public in-between spaces, addressing a long-standing methodological gap in urban design research.