CONTENTS 1. Introduction 1 2. Two- and three-wheelers and urban transport systems 1 2.1Two- and three-wheelers in developing Asian Cities 1 2.2Public transport issues 4 The outlook for a motorcycle city 4 2.3Road safety issues 5 3. The problem of two-stroke engine emissions 6 3.1Types of emissions 9 3.2Factors exacerbating emissions 10 Misuse of lubricant 10 Inadequate vehicle maintenance 10 Adulteration of gasoline 11 Lack of catalytic converters 11 3.3Impacts of emissions 11 Health impacts 11 Global warming impacts 11 3.4Reducing emissions from two-stroke engine vehicles 12 Vehicle technologies 12 Improving gasoline quality 14 Improving lubricant use 14 Improving maintenance 16 3.5 Alternatives to two-stroke gasoline engines 17 Four-stroke gasoline engines 18 Vehicles powered by Liquefied Petroleum Gas 19 Vehicles powered by Compressed Natural Gas 19 Electric vehicles 21 3.6Policy options 22 Promoting alternative modes of travel 22 Standards 22 Emissions based policies 23 Technology-specific policies 26 Economic and fiscal instruments 28 Raising public awareness 28 3.7Future directions 30 4. Further references 30 4.1References cited in the text 30 4.2Internet resources 31