Measuring Central Business District (CBD) walkability using intersection permeability and activity intensity

This paper develops a Central Business District (CBD)-specific walkability index to address limitations of standard metropolitan-wide indices that mischaracterize employment-dominant CBDs. The index is applied to CBDs in 50 U.S. state-representative cities using standardized 1-mile diameter CBD windows (land area excluding water). Network permeability is captured through densities of 4 + leg and 3-leg intersections, and activity intensity is represented by employment and population densities. To avoid penalizing legitimate job surpluses, a population-to-employment ratio adjustment is applied only when CBDs become unusually resident-heavy (T = 0.35, R_max = 10). Criterion weights, derived using the Analytic Hierarchy Process (CR = 0.013), are 0.46 (4 + intersection density), 0.14 (3-leg intersection density), 0.30 (employment density), 0.05 (population density), and 0.05 (resident-heaviness score). Validation uses commute mode shares for workers 16+, including walk-only and walk-plus-transit trips. A regression model with all five components explains walk + transit share well (R² = 0.752, n = 50). Rank agreement between the index and walk + transit shares is strong (Spearman ρ ≈ 0.75), and mean walk + transit shares drop sharply across index tiers. The method offers a transparent CBD walkability benchmark, highlighting the importance of connected street networks and mixed-use intensity.