关键词：空气污染；货运作业；排放量
摘 要：In recent years, corporations have shown increasing interest in measuring their environmental impacts, especially pollutant emissions. Business interests--for instance, preparing for imminent regulation--motivate this trend as much as ethics. Investors and customers factor environmental impact into their business decisions, and sustainable companies have a competitive advantage. According to Department of Transportation Climate Change Report, transportation greenhouse gas (GHG) emissions have been growing steadily in recent decades. From 1990 to 2006 alone, transportation GHG emissions increased 27 percent, accounting for almost one-half of the increase in total US GHG emissions for the period. Transportation GHG emissions account for 29 percent of total US GHG emissions, and over 5 percent of global GHG emissions. In 2006, emissions from on-road vehicles accounted for 79 percent of transportation GHG emissions. Emissions from trucks accounted for 19 percent. For companies with large distribution systems, emissions from transport operations constitute a significant portion of their environmental impact. Many models have been developed to estimate vehicle emissions, though the focus in research and in practice has been on automobiles, as opposed to trucks and other heavy vehicles. In addition, there is a lack of standards governing emissions reporting. Wide variations and lack of documentation make comparisons between companies or years difficult. The goal of this project is, therefore, to develop a rigorous, flexible, and practical framework for estimating the emissions of freight transport operations. To meet this goal, we developed a software tool based on simple, yet defensible and reliable economic models of marginal emissions contributions from individual shipments. The initial focus is on trucking, but extensions for other freight modes are possible.