We investigate the relationship between the extent of a city's subway network, its population and its spatial configuration. For the 632 largest cities in the world we construct panel data describing population, measures of centralization calculated from lights at night data, and the extent of...

We investigate the relationship between the opening of a city's subway network and its air quality. We find that particulate concentrations drop by 4% in a 10km radius disk surrounding a city center following a subway system opening. The effect is larger near the city center and persists over...

Gendron-Carrier et al. (2022) studies the effect of subway openings on urban air pollution. The authors find a null average effect, but a negative effect in cities with high initial pollution. In this comment, I perform several robustness checks on the negative effect for high-pollution cities,...