摘要：

Worldwide, greenhouse gas emissions are rising faster in transportation than in any other sector. Rapid motorization — more cars and trucks — is the principal cause. This report focuses on the challenges faced by developing countries in accommodating and managing motorization and the demand for improved transportation. Enhanced mobility has many positive effects on economic development and social welfare, including more efficient movement of goods and improved access to jobs, health services, and education. However, if enhanced mobility is achieved primarily through increased reliance on conventional private cars, it can mean diverting substantial financial resources to roads and suffering worse air pollution and traffic congestion. The benefits are enormous, but the costs can also be substantial. These positives and negatives are accentuated in the developing nations of Africa, Asia, and Latin America. Most are experiencing rapid population growth and urbanization, and many have fast-growing economies. The number of private vehicles is increasing in almost all developing countries. The challenges posed by motorization are unprecedented for these countries. When the more developed countries were building their transportation infrastructure, their populations were small compared to those in much of today's developing world, and the cost of motorized vehicles was relatively high. Today's megacities of the developing world are already huge and still expanding. There is little time or money to build public transportation systems or to expand roads to handle the new traffic. They are already experiencing serious congestion, economic and environmental damage, and major safety problems. Yet the problems are not uniform; each city and country faces different circumstances. This report provides a broad characterization of transportation in developing countries, identifying common challenges and opportunities for policymakers, and suggesting policy options that aim to slow the growth of greenhouse gas emissions from the transportation sector. The most important observations of this report are the following: Rapid motorization — and rapid growth in transportation-related greenhouse gas emissions — are unavoidable in most developing nations. Most developing countries today have low per capita transportation emissions, largely because few people have access to personal transportation. Rapid motorization is transforming transportation and accelerating increases in greenhouse gas emissions. The relationship between car ownership and income is not fixed. While it is true that income is the primary force of motorization — explaining perhaps half the growth in vehicle ownership — there is much variation in vehicle ownership among cities and countries at similar income levels. Once people have personal vehicles, they use them even if alternative transportation modes are available. This is because the variable cost of operating a vehicle is relatively low compared to the fixed cost of purchasing one. There are many sensible policies and strategies that would slow the growth of transportation sector greenhouse gas emissions. Key strategies include increasing the relative cost of using conventional private cars and enhancing the quality and choices of alternative transportation modes. Many of the strategies for slowing and eventually reducing greenhouse gas emissions from transportation have local as well as global benefits. Local benefits include reduced air pollution, less traffic congestion, and lower expenditures for road infrastructure. This report explores strategic paths and alternative futures that could break the link between economic and greenhouse gas emission growth in developing countries. Successful efforts underway in some developing countries — examples of which are highlighted in some of the case study reports that contributed to this overview — demonstrate that developing countries can forge a more sustainable transportation future. Is there a single city that can be looked to as a model for others? This report suggests

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