Logistics Performance and Transport Carbon Emissions: Evidence of a Logistics Sustainability Kuznets Curve

Background: This study develops the Logistics Sustainability Kuznets Curve (LSKC) to examine whether the relationship between logistics performance and transport carbon intensity changes across levels of logistics capability. Methods: An unbalanced panel of 565 observations from 126 economies across six World Bank Logistics Performance Index (LPI) waves (2010–2023) was analysed using linear, quadratic, two-way fixed-effects, endpoint-slope, exploratory breakpoint, nonlinear income, and robustness specifications. Transport energy CO2 emissions per million US dollars of GDP measure transport-wide rather than freight-only emissions. Results: The preferred fixed-effects estimates indicate a positive lower-end slope and downward curvature, with an implied turning point at LPI 3.55. The upper-end slope is negative but statistically insignificant. Adding nonlinear income produces a negative LPI-squared coefficient significant at the 5% level, while squared income remains insignificant. An exploratory breakpoint near LPI 3.05 suggests moderation, although the slope change is insignificant and the subsequent slope remains positive. Excluding 2023 reduces precision, while winsorisation preserves the nonlinear pattern. Conclusions: Findings support an expansion stage and emerging efficiency transition but do not establish a mature declining stage. The evidence suggests a logistics-specific nonlinear association without confirming a universal inverted U-shaped relationship.