This paper examines the impacts of measures to reduce emissions from buses, cars, and two-wheelers in Mumbai, India. We have considered three possible policies: conversion of diesel buses to CNG, an increase in the price of gasoline and a tax on vehicle ownership. Our results suggest that the most effective policy to reduce emissions from passenger vehicles—in terms of the total number of tons of PM10 reduced—is to convert diesel buses to CNG. The conversion of 3,391 diesel buses to CNG would result in an emissions reduction of 663 tons of PM10 per year, 14 percent of total emissions from transport.