Sustainable mobility in Italian regions. May private cars be replaced by mass transport means?

This paper investigates the extent of substitutability between private cars and mass transport means within the framework of sustainable mobility, introducing a novel theoretical perspective that models substitutability as a conditional and regionally heterogeneous behavioural response. Grounded in consumer choice theory and enriched with insights from behavioural economics, the study develops a microeconomic model where relative perceived quality is the key driver of modal shift. Using Italian NUTS-2 regional data, we construct original indicators of quality and apply a cascade Data Envelopment Analysis (DEA) to detect whether car usage responds as a substitute or complement to improvements in the quality of mass transport means. A Dynamic ARDL simulation further explores the effect of policy-driven quality enhancements through transport and R&D expenditure. Findings highlight substantial spatial variability: while some regions exhibit strong substitutability, others remain stuck in complementarity traps, despite policy interventions. The study contributes to the literature by operationalising conditional substitutability and linking empirical evidence with both infrastructural and behavioural policy implications. • Modal shift towards mass transport means depends on perceived quality. • Many Italian regions show no substitutability between private cars and mass transit. • The impact of public transport expenditure varies greatly across regions. • R&D fosters the shift only where transport systems meet user needs. • Behavioural and structural gaps hinder the shift in less developed regions.