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While great progress has been made over the past two decades in controlling emissions from motor vehicles, serious problems remain. Substantial growth in vehicles and poorer than expected in use performance have partially offset reductions achieved. While future gains must continue to take advantage of technological and fuel advances, special attention must be paid to in-use emissions and vehicle growth.

This study builds upon the National Academy of Sciences study in the rapidly changing area of diesel particulate cost-benefit analysis and updates it where appropriate based on new data or analysis. It does not generate new information but merely reviews and analyzes existing data. The body of the paper a) explains the basis for estimating the various costs, b) describes a computer model to relate the costs to the benefits, and c) presents the results of the analysis.

Despite progress in air quality for many conventional pollutants, the São Paulo Metropolitan Region continues to exceed health-based standards for particulates and ozone. In 1986, the Federal government established the Vehicle Air Pollution Control Program (PROCONVE), which created tighter emissions standards for all new vehicles and mandated improved fuel quality. As a result, considerable progress has been made with regard to certain pollution problems, particularly with carbon monoxide (CO) and sulfur dioxide (SO2). Two pollutants continue to threaten public health in São Paulo: particulate matter (PM) and ozone. For particles, standards are set and a monitoring program is in place for PM10 (particles of 10 μm or smaller, also known as inhalable PM). PM10 concentrations in São Paulo continue to exceed air quality standards on a regular basis.

Worldwide concerns with global climate change and reducing oil consumption have increased interest in expanding the global light duty diesel penetration, adding to the already dominant role of diesels in commercial vehicles. The major impediment has been concern over the adverse health effects associated with diesel exhaust. This paper will review the status of these concerns, summarizing recent studies conducted by the World Health Organization, the US EPA and the California Air Resources Board. In response to these concerns, various countries have adopted controls on both diesel vehicles and engines and their fuels. The current status of these efforts as well as the state of control technology will be summarized.

High mileage vehicles (in excess of 50,000 miles) contribute more than half of all vehicular emissions. With the new catalytic converter equipped cars, the proportional contribution of these vehicles may be even higher than for pre-catalyst vehicles. Thus a substantial portion of motor vehicle related air pollution may be caused by vehicles not subject to the manufacturer directed provisions of the Clean Air Act. This paper presents a modeling effort based on hypotheses and some preliminary data, and suggests some alternatives to combat this potential problem.

Progress of the Federal program for control of pollutant emissions from motor vehicles is summarized, through the 1968-1980 period. The standards mandated by the Clean Air Act have now been achieved. The future will see greater emphasis on maintaining the control of emissions from passenger cars in service, as opposed to more stringent emissions standards for new cars. More emphasis will also be placed on standards for highway vehicles other than passenger cars and on control of added pollutant types, such as particulate emissions from diesel powered vehicles.

Over the past century, huge amounts of air pollutants and gases have been released into the atmosphere that now pose risks to human health, natural ecosystems, and the earth's climate. Motor vehicles are a major contributor to both the build-up of greenhouse gases -- potentially the most serious of these problems -- and the creation of urban smog and acid rain. The purpose of this paper is to summarize the nature of these problems and the role played by motor vehicles in causing them. The significance of pollutants other than CO2 which are emitted in large quantities from vehicles will be shown to be important for global warming. Further, the increasing significance of vehicles produced or registered in rapidly expanding countries will be assessed. Finally, the growing importance of vehicle modes other than passenger cars will be summarized.

Two opposing trends with significant implications for the future growth of diesel vehicles and engines are taking place -an increased focus on small particles and ozone levels as serious causes of adverse effects on health and the environment and concerns regarding global warming and the need to lower carbon dioxide emissions. The purpose of this paper is to summarize developments with regard to both of these areas and to highlight the emerging concerns with the number and size of so called ultrafine particles and high in use NOX emissions from US heavy duty trucks.

Driven in part by concerns regarding global warming, there is a clear trend toward increased sales of light duty diesel vehicles in many parts of the world. This trend can result in many positive environmental benefits including low fuel consumption, and therefore low levels of CO2, low levels of exhaust CO and HC (especially during cold start conditions), and very low levels of evaporative hydrocarbons. However, increased diesel sales have a downside, relatively high NOx and particulate emissions. These pollutants continue to receive high priority attention in most areas of the world. As a result, countries around the world are increasingly tightening diesel regulations with the result that technology for reducing emissions continues to advance. Engine and combustion improvements have substantially reduced NOx and particulate from modern engines.

Driven in part by concerns regarding global warming, there is a clear trend toward increased sales of light duty diesel vehicles in many parts of the world. This trend can result in many positive environmental benefits including low fuel consumption, and therefore low levels of CO2, low levels of gaseous exhaust CO and HC (especially during cold start conditions), and very low levels of evap orative hydrocarbons. However, increased diesel sales have a downside, relatively high NOx and particulate emissions. These pollutants continue to receive high priority attention in most areas of the world. As a result, countries around the world are increasingly tightening diesel regulations with the result that technology for reducing emissions continues to advance. The variety of regulatory approaches being pursued to reduce diesel NOX and particulate by countries around the world will be reviewed and summarized.

Across the entire globe, there has been tremendous movement toward the further control of diesel vehicle emissions over the past 1 to 2 years. With regard to heavy duty vehicles, the EU in late 1999 finalized requirements for Euro 3, Euro 4 and Euro 5, to be phased in by 2008. These requirements are expected to require the introduction of advanced PM and NOx controls. The US EPA has adopted even more stringent requirements to be introduced in 2007 along with very low sulfur (<15 PPM) diesel fuel. Japan is in the process of an intense review which will likely reduce fuel sulfur levels to at least 50 PPM and introduce substantially tighter PM requirements by 2005. They are also developing a major diesel retrofit program. With regard to light duty vehicles, the California Air Resources Board has established the principle that diesel fueled vehicles should meet the same standards as gasoline fueled vehicles and the US EPA followed suit with its Tier 2 program.

As the diesel population continues to grow in various parts of the world, and as concerns regarding diesel particulate effects on public health and the environment increase, more and more countries are adopting tighter and tighter standards. The purpose of this paper is to review the current status of such regulation around the world.

The purpose of this paper is to survey the adverse environmental impacts resulting from motor vehicles, to review technologies developed to address these problems, and to summarize the current status of pollution control programs around the world.

Rapidly industrializing developing countries are now starting to note similar air pollution problems to those of the industrialized world. This paper surveys the adverse environmental impacts resulting from motor vehicles, reviews technologies developed to address these problems, and summarizes the current status of pollution controls around the world. Special focus is on the design of strategies to address the emerging problems of developing countries.

At the present time, as the world's vehicle population inches over 700 million, countries around the world are continuing to struggle with their motor vehicle pollution problems. Some countries have made great progress in reducing CO and HC emissions from vehicles, and to a lesser extent NOX, in spite of substantial growth in their vehicle populations. While car standards continue to be pushed, the motor vehicle focus is gradually shifting to heavy duty trucks and buses and off road vehicles and engines. Fuels improvements are also playing an increasingly important role. Finally, concerns with CO2 and other greenhouse gases are getting increased attention. The purpose of this paper will be to provide a broad overview of these developments, highlighting the successes achieved to date and the future challenges.

Over the course of the past five decades, as the vehicle population around the world has exploded, a great deal has been learned about the implications for the local, regional and global environment. A great deal of effort has been focused on addressing the local and regional problems with some success but continued growth has offset some of these gains. In recent years, global pollution concerns have increased and the motor vehicle contribution has been found to be increasingly important. The thrust of this paper would be a review of the developments to date around the world and a focus on remaining problems such as toxic emissions, global warming and in use emissions performance.

Motor vehicles already play a significant role in the climate modification problem and have the potential to play an even greater role in the future. The vast majority of the world's vehicles are concentrated in the highly industrialized areas of Western Europe and North America, but an increasing proportion are being produced in the Asia Pacific region and a large and growing proportion of them remain in that area. The purpose of this analysis is to examine the environmental implications of the current vehicle fleet and its likely future directions. An overall policy will be proposed to address both local and global environmental concerns

This paper will review the potential need for and environmental gains from the use of alternative fuels in vehicles to address urban air pollution. Then the global warming problem and the role of motor vehicles presently and in the future will be assessed. Finally, the positive and negative consequences of alternative fuels from this perspective will be analyzed. In summary, this paper will show that while there are potentially significant concerns, if appropriate government policies are adopted alternative fuels have the potential to substantially improve both local and global environmental problems and should be a key element of both strategies.

Areas of rapid Industrialization in Asia are now starting to experience unacceptable air quality or are projecting that they will in the relatively near future as a result of rapid growth in their vehicle populations. In addressing these problems, there is much that can be learned from the experience and mistakes of the industrialized world. In addition, however, there are some unique problems of developing countries, especially certain of the smaller ones in Asia, which would seem to benefit from special approaches. The purpose of this paper is to briefly survey the adverse environmental impacts resulting from motor vehicles, to review technologies developed to address these problems, and to summarize the current status around the world. Special focus will be on the development of strategies to address the emerging problems of developing countries in Asia.

Motor vehicles account directly for up to one-sixth of the total H-ion deposition in the Eastern United States and substantially more in the West. Vehicular pollutants may also play an important catalytic and synergistic role in acidic deposition. In addition, however, motor vehicles clearly cause or contribute in a major way to ozone, hydrocarbons, lead, total nitrogen and other transported air pollutants. It is increasingly clear that whether the goal is to reduce acid rain specifically or transported air pollutants generally, increased control of motor vehicle emissions is important and perhaps essential.