Large cities are less efficient for sustainable transport: The ABC of mobility

TL;DR

This study models urban mobility using an ABC framework across nearly 800 cities, revealing regional differences in car dependency, with US cities heavily reliant on cars regardless of size, and income strongly influencing automobile use.

Contribution

It introduces a novel ABC triplet model to analyze city mobility patterns and provides a comprehensive cross-regional analysis of factors affecting car dependency.

Findings

Outside the US, larger cities favor public transport and active mobility.

US cities show 90% car dependency regardless of size.

Higher income correlates with increased automobile use.

Abstract

The use of cars in cities has many negative impacts on its population, including pollution, noise and the use of space. Yet, detecting factors that reduce automobile dependency is a serious challenge, particularly across different regions. Here we model the use of different modes of transport in a city by aggregating active mobility (A), public transport (B) and cars (C), thus expressing the modal share of a city by its ABC triplet. Data for nearly 800 cities across 60 countries is used to model car use and its relationship with city size and income. Our findings suggest that outside the US, longer distances experienced in large cities reduce the propensity of active mobility and of cars, but public transport is more prominent. For cities in the US, roughly 90\% of its mobility depends on cars, regardless of city size. Further, income is strongly related to automobile dependency. Results show that a city with twice the income has 37\% more journeys by car.