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City-level policies are increasingly recognized as key components of strategies to reduce transport greenhouse gas emissions. However, at a global scale, their total efficiencies, costs, and practical feasibility remain unclear. Here, we use a spatially-explicit urban economic model, systematically calibrated on 120 cities worldwide, to analyze the impact of four representative policies aiming at mitigating transportation GHG emissions, also accounting for their economic welfare impacts and health co-benefits. Applying these policies in all cities, we find that total transportation GHG emissions can be reduced by 28% in 15 years, compared with the baseline scenario. However, the consequences of the same policies vary widely between cities, with specific effects depending on the policy considered, income level, population growth rate, spatial organization, and existing public transport supply. Impacts on transport emissions span from high to almost zero, and consequences in terms of welfare can either be positive or negative. Applying only welfare-increasing policies captures most of the emission reductions: overall, they reduce emissions by 20% in 15 years. Our results highlight that there is no one-size-fits-all optimal policy to mitigate urban transport emissions but that cities can match their specific situation with a selection of mitigation policies: hence, we call for global climate mitigation models to better represent heterogeneity across cities.

International audience; Urban green spaces provide cultural ecosystem services, and urban policies typically aim to enhance these services by targeting new investments in deprived areas. The implementation of urban greening policies is one way to reduce inequalities in well-being, for example by targeting areas where increased access to green spaces will benefit citizens of low socioeconomic status. Most research has addressed the targeting of green infrastructure development by considering income and access to green spaces, while few studies have considered a multidimensional definition of well-being. The aims of this paper are to i) integrate inputs from the economic and political philosophy literature to propose a broader definition of well-being, including health, education, insecurity, and social relations; ii) develop a criterion to prioritise areas where urban greening would have the greatest impact on well-being inequalities; and iii) apply this criterion to the Paris metropolitan area (Ile-de-France region), a spatially heterogeneous region where areas deprived of access to green spaces are not systematically deprived in other dimensions. Our analysis shows that the city of Paris and the inner suburbs would be targeted when considering inequality in access to green spaces only. The results differ when inequalities in income or multidimensional well-being are taken into account, in which case the northern inner suburbs and some outer suburbs become a higher priority.

Using a unique dataset containing gridded data on population densities, rents, housing sizes, and transportation in 192 cities worldwide, we investigate the empirical relevance of the monocentric standard urban model (SUM). Overall, the SUM seems surprisingly capable of capturing the inner structure of cities, both in developed and developing countries. As expected, cities spread out when they are richer, more populated, and when transportation or farmland is cheaper. Respectively 100% and 87% of the cities exhibit the expected negative density and rent gradients: on average, a 1% decrease in income net of transportation costs leads to a 21% decrease in densities and a 3% decrease in rents per m2. We also investigate the heterogeneity between cities of different characteristics in terms of monocentricity, informality, and amenities.