Mobility Inequalities and Urban Poverty: A Decomposition of Travel Speed Differentials in France (2008–2019)

Observed travel behaviours are widely used to assess mobility inequalities, but the mechanisms underlying these inequalities remain insufficiently understood. Viewing travel speed as a measure of efficiency in overcoming spatial friction, this research analyses travel-speed differentials between residents of deprived neighbourhoods and the broader urban population in France. Using instrumental-variable regressions with robust standard errors, we compute Blinder-Oaxaca decompositions based on the 2008 and 2019 French National Travel Surveys. Travel speeds in deprived neighbourhoods are substantially lower, and the gap is mainly explained by compositional factors. The primary driver is lower car use, combined with greater reliance on walking and, to a lesser extent, public transport. Urban structure also plays a significant role, as residents of these areas travel more frequently in lower-speed environments. Three complementary analyses are performed. The first shows that modal disparities stem predominantly from vehicle availability and suggests a possible "neighbourhood effect" in 2019, absent in 2008. The second reveals that speed disparities widened sharply over the decade, a divergence largely explained by the included variables. The third shows that modal disparities vary substantially across distance bands and over time. Enhancing alternative mobility options for low-income groups could constitute a sustainable and equitable policy direction.