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.

翻译：为实现净零排放目标，城市必须减少对私家车的依赖。然而，以汽车为中心的城市发展将汽车从便利工具转变为获取基本服务的必需品，形成了严重的"汽车依赖"。本研究提出了一种新型汽车依赖指数（CDI），量化了欧洲和北美18个城市中私家车与公共交通之间的可达性差距。利用高分辨率地理空间数据和数值模拟，我们发现显著的空间不平等性——即使在考虑收入因素后，汽车依赖仍是驱动汽车保有量的首要因素。针对罗马规划中的地铁扩建进行的"假设情景"模拟预测可减少约6万辆通勤车辆，但突显出孤立干预措施仅能产生局部影响。我们得出结论，系统性、网络级的公共交通扩展对于瓦解汽车依赖体系、构建公平可持续的城市交通至关重要。该框架为政策制定者提供了客观且可扩展的工具，可有效识别适宜构建无车区域的区域并优化基础设施投资。