Is car traffic close to saturation in France?

Abstract

After decades of uninterrupted growth, car traffic temporarily levelled off during the 2000′s in France, before coming back to growth after 2008. However, there are reasons to believe that car traffic growth is potentially limited, among which completion of the diffusion process for car ownership, limited travel time budgets, decreasing returns of additional car travel. In this study, we implement a disaggregate model at the household level to project future car ownership and car mileage per household in France, along with total car traffic, accounting for demographic growth. Our model relies on a sequential approach using panel data, with an ordered response probit model for the number of vehicles, including saturation thresholds by vehicle rank, and a log-linear model for car mileage, conditional on the number of vehicles, both with correlated random effects. A time trend is also incorporated to account for the decreasing household car mileage that was noticed over the last twenty years, which is not entirely explained by decreasing household size and the gradual decline of income growth. Assuming this trend to go on, total car traffic in France would grow only a little by 2050, despite demographic growth, and start decreasing from 2040. We discuss these results by questioning the structural nature of this trend.