Policy rigidity or local innovation? High-speed rail, mandatory pressure and green growth in Chinese cities

Utilizing panel data from 281 Chinese cities spanning 2007-2018, this study empirically examines the impact of high-speed rail (HSR) opening on urban green growth and its underlying mechanisms from the perspective of mandatory isomorphism theory. The findings reveal that HSR, overall, significantly promotes urban green growth, particularly in environmentally key cities, non-resource-based cities, cities within urban agglomerations, and cities with weak infrastructure. This positive effect strengthened after 2012. Spatial econometric analysis further indicates that while HSR exerts a positive direct effect locally, it generates significant negative spillovers on neighboring cities. The core mechanism lies in HSR significantly enhancing the transmission of environmental regulatory pressure from the central government to local governments (mandatory isomorphism) by compressing regulatory distance. Under such pressure, local governments adopt varying coping strategies, ranging from rigid policy enforcement to proactive localized innovation. However, this pressure is a "double-edged sword": in resource-based cities and low-infrastructure cities with weaker institutional resilience and capacity, excessive regulatory pressure can inhibit green growth, triggering "problemistic search" behaviors. Mediation tests confirm the dual role of regulatory pressure, which serves as a significant suppressant in vulnerable cities despite the net positive effect of HSR. This research provides critical insights for policymakers: to maximize the green transformation benefits of HSR, it is essential to implement differentiated policies precisely, optimize the environmental regulatory toolbox, and establish dynamic assessment mechanisms. This will synergistically advance the goals of transport infrastructure investment with Sustainable Cities (SDG 11) and Climate Action (SDG 13). • HSR, overall, significantly promotes urban green growth, particularly in environmentally key cities, non-resource-based cities, cities within urban agglomerations, and cities with weak infrastructure. • HRS compresses regulatory distance, intensifying mandatory isomorphic pressure from the central government, which shapes local environmental governance strategies ranging from policy rigidity to localized innovation. • While HSR enhances mandatory environmental regulatory pressure, this pressure itself suppresses green growth in cities with weak institutional resilience , revealing a negative mediation pathway. • HSR operation in one city reduces green growth in neighboring cities by approximately 2.1%, highlighting regional inequalities in the benefits of transport infrastructure. • Tailored support for vulnerable cities, optimized regulatory toolkits, and dynamic assessment mechanisms are essential to maximize HSR’s green benefits and support SDGs 11 and 13.