We study the optimal and equilibrium size of cities in a city system model with environmental pollution. Pollution is …, if pollution is local or per capita pollution increases with population, we find that equilibrium cities are too large …. When pollution is global and per capita pollution declines with city size, however, equilibrium cities may be too small …

The paper studies the effect of public transport policies on urban pollution. It uses a quantitative equilibrium model … with residential choice and mode choice. Pollution comes from commuting and residential energy use. The model parameters … transport coupled with increasing transit speed affects the equilibrium. In the baseline simulation, total pollution falls by 0 …