We thank Zmarak Shalizi and Gunther Schramm for very useful comments. We also thank Roula Yazigi for excellent assistance. The findings, interpretations, and conclusions expressed in this paper are entirely those of the authors. They do not necessarily represent the views of the World Bank, its Executive Directors, or the countries they represent. The paper should not be cited without the permission of the This paper develops a simple framework to analyze various pollution control strategies that have been used or are proposed in the urban passenger transport sector. The context is the declining quality of air in urban areas, which is among the serious problems associated with the rapid motorization of societies the world over. 1 The paper examines the point of impact of different policy levers and provides a categorization of