Car Dependency in Urban Accessibility

TL;DR

This paper presents a new Car Dependency Index to measure accessibility disparities in cities, revealing spatial inequalities and emphasizing the need for systemic transit expansion to reduce reliance on private vehicles.

Contribution

Introduces a novel Car Dependency Index and a geospatial framework to quantify and analyze car dependency and accessibility gaps in urban areas.

Findings

Car dependency persists despite income considerations.

Planned metro expansion in Rome could reduce 60,000 commuting vehicles.

Isolated interventions have limited, localized impacts.

Abstract

To achieve net-zero emissions, cities must transition away from reliance on private vehicles. However, car-centric urban growth has transformed the automobile from a convenience tool into a necessity for accessing essential services, creating significant "car dependency". This study introduces a novel Car Dependency Index (CDI) that quantifies the accessibility gap between private and public transport across 18 cities in Europe and North America. Utilising high-resolution geospatial data and numerical simulations, we reveal pronounced spatial inequalities, showing that car dependency remains a primary driver of car ownership even when accounting for income. A ``what-if" simulation of the planned metro expansion in Rome predicts a reduction of approximately 60,000 commuting vehicles, yet highlights that isolated interventions have localised impacts. We conclude that systemic, network-level transit expansions are essential to dismantle car-based systems and foster equitable, sustainable urban mobility. Our framework provides policymakers with an objective, scalable tool to identify viable areas for car-free zones and target infrastructure investments effectively.