Motorized individual mobility in commuting trips: modal preference or constrained mode choice? A machine learning approach

In the Ile-de-France Region, France, the modal share of car in commuting trips is 42% (Source: Global Transport Survey, 2010), a much lower figure than the national average (70%). In this article, we use an original predictive tool that relies on multi-source input data to estimate the flows, modes, and socio-demographic characteristics of mobility users. We focus on commuting, as the recurrence of such trips theoretically enhances modal shift towards more sustainable transport modes on the long term. From the output data predicted by the tool, we elaborate, for all origin-destination couples (O-D) between municipalities in the Ile-de-France Region (n = 1286²), an original indicator of the relative performance of public transport in relation to car. We measure this indicator as compared travel times: for each O-D couple, we compare the predicted travel time to the modal share of car, also predicted by our tool. We thus identify three groups of municipalities:-A first group whose respective modal shares of car and public transport are consistent with the modal performance indicator: comparable travel times between car and public transport are correlated with respective modal shares close to the Ile-de-France average;-A second group whose residents seem more favorable to public transport than suggested by the modal performance indicator, as predicted travel times appear to be in favor of car;-A third one, with the opposite conclusions. A more detailed territorial analysis focuses, in a second time, to cross these three groups of municipalities with the following typology of territories: Paris (central city), other municipalities of Greater Paris (inner suburbs), other municipalities of the Paris agglomeration (outer suburbs), central municipalities of the rest of the Ile-de-France Region, other municipalities. This typology crosses dwelling densities, employment densities and flows between the two on the one hand, and a morphological criterion delimiting the boundaries of the agglomeration, on the other hand. The interest of such a crossover lies in mobility issues that remain specific, within the Ile-de-France, to each type of area. Such results highlighting modal preferences of households appear valuable for social sciences, in that they allow to empirically raise the calibration difficulties often pointed at in theoretical models of urban economics.