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3 CHAPTER 1 Introduction and Research Summary 1.1 Objective Chapter 5: provision of five research statements to im- prove the estimation of freight transportation emissions. The objective of this report is to review and evaluate current methods used to estimate air emissions from freight trans- portation activities and determine their suitability for decision 1.3 Study Framework making and public education. All freight modes are repre- This report is organized by transportation mode, since many sented, including heavy-duty trucks, rail, ocean-going vessels, emission models and methods to estimate freight emissions harbor craft, cargo handling equipment, and air freight. To the are specific to each mode. Three elements are discussed for extent possible, three geographic scales are analyzed for each each mode: mode, namely at the national, regional, and local/project levels. The regional scale can apply to areas within one state or areas Methods: the most currently applicable and widespread comprising multiple states. methods to estimate and forecast freight emissions in the public domain are discussed and evaluated. A method is de- 1.2 Report Organization fined as a step-by-step approach on how to estimate vehicle and freight activity, how to develop emission factors, and This report is organized as follows: how to calculate freight emissions. A method generally in- cludes the use of several input parameters, as well as one or Chapter 1: report summary including objectives, report more models; organization, study framework, and a summary of each Models: current models used to estimate freight activity, subsequent chapter; emission factors, and total emissions; and Chapter 2: detailed discussion of how freight emissions Parameters: input parameters are used in both methods estimates are used and applied by public- and private-sector and models to define fuel and vehicle/vessel characteristics, stakeholders; estimate emission factors, and calculate emissions. Chapter 3: detailed review of the current state of the prac- tice for estimating freight emissions across all modes and The complexity, accuracy, and precision of methods, mod- geographic scales, and evaluation of current methods and els, and input parameters depend on the following three factors: models used to estimate emissions from freight transporta- tion, including an analysis of strengths and weaknesses of Magnitude of mode emissions: all else being equal, it is ex- the main methods and models, an assessment of process pected that modes with the greatest emissions will have uncertainty of these methods and models, and an assess- more data available, better documented methods, and more ment of parameter uncertainty related to the inputs required established models. As a result, methods, models, and input by these methods and models; parameters to estimate trucking emissions tend to be more Chapter 4: development of a Conceptual Model for freight detailed than for other modes; transportation activity as it relates to emissions calculations. Data collection process: the data collection process has an The Conceptual Model offers a comprehensive represen- effect on the level of detail, complexity, and accuracy of tation of freight activity in the United States, covering all data. The data collection process is influenced by (1) the modes and relationships between modes; and number of freight activity generators, (2) the regulatory