Nonlinear relationship of urban traffic congestion with rainfall and mediating effects on metro ridership: a comparison study of Guangzhou and Shenzhen
▻https://www.frontiersin.org/journals/sustainable-cities/articles/10.3389/frsc.2026.1871487/full
Rainfall increasingly stresses urban road networks, yet how congestion responds across the full range of rainfall intensity, and how that response propagates to rail transit, remains incompletely understood. Drawing on daily data on rainfall, a road Traffic Congestion Index (TCI), and metro ridership in two major cities of the Guangdong-Hong Kong-Macao Greater Bay Area, Guangzhou and Shenzhen, this study fits penalized spline generalized additive models with day-type and seasonal controls, and then employs causal mediation analysis with metro ridership as the key mediating variable to decompose how rainfall’s effect on road congestion propagates to rail transit. Congestion in Guangzhou rises continuously and does not saturate within the observed range (net increment over 20–60 mm of (…)