Motor vehicles are major contributors to severe air pollution problems everywhere. As the vehicle fleet continues to grow, the effectiveness of current emissions control policies in OECD countries is being undermined, while a number of highway pollutants, notably carbon dioxide, remain unaddressed. This report seeks to determine the impact that stricter, comprehensive control programmes could have on motor vehicle emissions over the next thirty to forty years. It examines the substantial potential for reducing emissions offered by state of the art control technology, but also underlines the crucial importance of preventive approaches for any long term strategy. A detailed series of recommendations is included to help policy makers design control programmes capable of reducing motor vehicle emissions over the long term.