Introduction
The development of transportation infrastructures has played a key role in the industrialization of national economies and the development of a global economy. Rapid and economically efficient transportation of passengers, raw materials, and finished goods has become essential to the functioning of the linked economies of Mexico, the United States, and Canada. Although the transportation systems of these countries have brought great economic benefits, they also have led to considerable environmental costs. Emissions from this sector produce local and regional air pollution such as photochemical smog, particulates, and acid rain. On a global scale, the transportation sector contributes to the continued buildup of greenhouse gases in the atmosphere.
Over the past several decades, considerable resources have been expended to combat such untoward consequences of transport activity. But many have questioned whether sufficient progress is being made, and whether new approaches may be needed to guide the development of the transportation system in an environmentally sustainable manner. This issue is becoming more important in developing countries such as Mexico, which are increasingly adopting more energy-intensive technologies. The issue also remains high on the policy agendas of industrialized countries like the United States and Canada, where continued increases in passenger and freight transport are offsetting the environmental gains made by improved technology.
There is, of course, much work being done to analyze the pollution problems caused by the transportation sector. But much of this work tends to be compartmentalized, considering discrete parts of the overall problem, i.e., specific pollutants, specific impact end points, single modes of transportation, or relatively short time horizons. This trilateral workshop was organized as a first step in developing a more comprehensive understanding of these issues. Workshop participants sought to anticipate how the structure of the North American transportation system will change over the next several decades, and what would be the impacts of these changes on the atmosphere and, in turn, on human and ecosystem health. They sought to address the following questions about the transportation sector — what is the probable path and the desirable path of evolution, and how do we put the right elements in place to ensure that the desirable path is the probable path?
