Patterns of car dependency of metropolitan areas worldwide: Learning from the outliers

Despite the development of alternative modes of urban transport, the private car is still the most popular transport option in many regions around the world. Various spatial and socio-economic characteristics of metropolitan areas (MAs) seem to be generally correlated with levels of car use, and thus with car dependency. In this research, we study car dependency in a subgroup of global MAs, that are characterized profiles of car dependency, and are therefore considered outliers. Drawing on data that are available from the Mobility in Cities Database (MCD), we consider 56 MAs and use Mahalanobis distance to identify 7 outlier MAs that are either more, or less car dependent than anticipated by the regression model. We investigate the driving forces behind unpredicted levels of car use and position the outlier MAs in a catalogue of mobility profiles. A combination of urban form, convenience of car use, availability of alternative modes to car and car ownership characteristics were found to contribute to the level of car dependency in these MAs.