Fig. 3: Private vehicular operations reported in the Millennium Cities Database for Sustainable Transport.

Global distribution of cities included in the Millennium Cities Database for Sustainable Transport. This figure shows the geographic coverage of the Millennium Cities Database for Sustainable Transport (MCD), compiled by the International Association of Public Transport (UITP). Each red location pin on the map represents a city included in the MCD dataset, which comprises cross-sectional data on urban transport and land use indicators from the year 1995. A total of 100 cities across all inhabited continents are represented in the dataset. The map highlights the broad global scope of the MCD, with a strong concentration of cities in Europe, North America, East Asia, and Oceania. Additional coverage spans major metropolitan areas in Latin America, Africa, South Asia, and the Middle East, ensuring a wide diversity in terms of development levels, geography, and urban form. The red pins mark the cities for which the MCD provides information on energy consumption, infrastructure characteristics, and other transport energy use-related metrics. However, due to missing or incomplete data for some variables in a subset of cities, only 84 cities from 42 countries were retained for the analysis of private vehicle energy consumption. The selection process ensured the analytical sample remained representative of different urban typologies while maintaining data quality. This figure is used to contextualise the spatial diversity of the cities included in the estimation of road transport energy use. The global spread supports comparative analysis and cross-regional insights, although the single-year nature of the dataset limits temporal inference. Despite its age, the MCD remains one of the most comprehensive and internationally harmonised sources of urban transport data, offering a valuable empirical foundation for understanding the structural drivers of energy demand in private vehicle use.