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Representing Freight in Air Quality and Greenhouse Gas Models (2010)

Chapter: Chapter 2 - Application of Freight Emissions

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Suggested Citation:"Chapter 2 - Application of Freight Emissions." National Academies of Sciences, Engineering, and Medicine. 2010. Representing Freight in Air Quality and Greenhouse Gas Models. Washington, DC: The National Academies Press. doi: 10.17226/14407.
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Suggested Citation:"Chapter 2 - Application of Freight Emissions." National Academies of Sciences, Engineering, and Medicine. 2010. Representing Freight in Air Quality and Greenhouse Gas Models. Washington, DC: The National Academies Press. doi: 10.17226/14407.
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Suggested Citation:"Chapter 2 - Application of Freight Emissions." National Academies of Sciences, Engineering, and Medicine. 2010. Representing Freight in Air Quality and Greenhouse Gas Models. Washington, DC: The National Academies Press. doi: 10.17226/14407.
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Suggested Citation:"Chapter 2 - Application of Freight Emissions." National Academies of Sciences, Engineering, and Medicine. 2010. Representing Freight in Air Quality and Greenhouse Gas Models. Washington, DC: The National Academies Press. doi: 10.17226/14407.
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Suggested Citation:"Chapter 2 - Application of Freight Emissions." National Academies of Sciences, Engineering, and Medicine. 2010. Representing Freight in Air Quality and Greenhouse Gas Models. Washington, DC: The National Academies Press. doi: 10.17226/14407.
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Suggested Citation:"Chapter 2 - Application of Freight Emissions." National Academies of Sciences, Engineering, and Medicine. 2010. Representing Freight in Air Quality and Greenhouse Gas Models. Washington, DC: The National Academies Press. doi: 10.17226/14407.
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Suggested Citation:"Chapter 2 - Application of Freight Emissions." National Academies of Sciences, Engineering, and Medicine. 2010. Representing Freight in Air Quality and Greenhouse Gas Models. Washington, DC: The National Academies Press. doi: 10.17226/14407.
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Suggested Citation:"Chapter 2 - Application of Freight Emissions." National Academies of Sciences, Engineering, and Medicine. 2010. Representing Freight in Air Quality and Greenhouse Gas Models. Washington, DC: The National Academies Press. doi: 10.17226/14407.
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Suggested Citation:"Chapter 2 - Application of Freight Emissions." National Academies of Sciences, Engineering, and Medicine. 2010. Representing Freight in Air Quality and Greenhouse Gas Models. Washington, DC: The National Academies Press. doi: 10.17226/14407.
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Suggested Citation:"Chapter 2 - Application of Freight Emissions." National Academies of Sciences, Engineering, and Medicine. 2010. Representing Freight in Air Quality and Greenhouse Gas Models. Washington, DC: The National Academies Press. doi: 10.17226/14407.
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Suggested Citation:"Chapter 2 - Application of Freight Emissions." National Academies of Sciences, Engineering, and Medicine. 2010. Representing Freight in Air Quality and Greenhouse Gas Models. Washington, DC: The National Academies Press. doi: 10.17226/14407.
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Suggested Citation:"Chapter 2 - Application of Freight Emissions." National Academies of Sciences, Engineering, and Medicine. 2010. Representing Freight in Air Quality and Greenhouse Gas Models. Washington, DC: The National Academies Press. doi: 10.17226/14407.
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Suggested Citation:"Chapter 2 - Application of Freight Emissions." National Academies of Sciences, Engineering, and Medicine. 2010. Representing Freight in Air Quality and Greenhouse Gas Models. Washington, DC: The National Academies Press. doi: 10.17226/14407.
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Suggested Citation:"Chapter 2 - Application of Freight Emissions." National Academies of Sciences, Engineering, and Medicine. 2010. Representing Freight in Air Quality and Greenhouse Gas Models. Washington, DC: The National Academies Press. doi: 10.17226/14407.
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16 This chapter documents the ways that freight transportation emissions are applied to support decisions on public policy, infrastructure investments, and transportation system opera- tions. A solid understanding of how freight emissions estimates are used is necessary in order to assess the uncertainties and potential sources of error in the emissions estimation process. In many cases, freight emissions estimates are prepared in response to federal or state regulations. These include the National Environmental Policy Act (NEPA) and similar state laws, the Clean Air Act and National Ambient Air Quality Stan- dards (NAAQS), and federal conformity regulations. In other cases, freight emissions estimates are used in non-mandatory studies that serve to educate stakeholders and guide government programs or policy. Freight emissions estimates are used in several basic ways. In some instances, the emissions estimates themselves are reported and used by stakeholders to inform decisions. In other cases, emissions estimates are fed into air quality dispersion models, which then may feed exposure estimates and health risk assessments. In many applications, freight emissions are combined with emissions from other mobile sources, or even with point and area sources, before they are processed and reported. In these cases, the impact of the freight component of the emissions on the ultimate decision may not be clear. The set of applications described in this section is by no means comprehensive. The applications included in this section are intended to be the most common and prominent, but the use of freight emissions estimates is almost limitless. 2.1 National- and State-Scale Applications National- and state-scale applications of freight emissions include GHG estimates as part of the EPA GHG Inventory (1) and state climate action plans, as well as national- and state-scale studies of the health impacts of pollutant emissions. 2.1.1 EPA GHG Inventory Freight transportation is a significant contributor to U.S. GHG emissions, contributing 26% of transportation GHG emissions and 7% of total U.S. GHG emissions in 2005. (1) These emissions are reported in the official EPA GHG Inventory, which is prepared annually by the EPA. Preparation of the inventory fulfills the U.S. commitment as a signatory to the United Nations Framework Convention on Climate Change. The EPA GHG Inventory reports six primary GHGs identified by the IPCC; three of these—CO2, N2O, and CH4— are produced by, and reported for, the transportation sector. The GHG inventory reports these emissions by year (going back to 1990), fuel, and vehicle type. Some of the fuel/vehicle categories encompass entirely freight sources (e.g., medium- and heavy-duty trucks); others encompass both freight and nonfreight sources (e.g., rail, commercial aircraft). As a complement to the EPA GHG Inventory, EPA has also conducted studies that examine transportation GHG emissions in greater detail, including an examination of trends for each mode and projections. (12) Another EPA-sponsored research study examined the causes for the rapid increase in freight- related GHG emissions since 1990. (13) The purpose of the National GHG Inventory is to provide a common and consistent mechanism for all nations to estimate emissions and compare the relative contribution of individual sources, gases, and nations to climate change. The EPA GHG Inventory and complementary studies do not directly affect decisions regarding public policy or infrastructure investment. The studies do influence federal programs, however, including EPA programs targeting the freight sector. For example, in the early part of this decade, EPA used inventory data to highlight the contribution of trucking to GHG emissions, which contributed to the development of the voluntary SmartWay freight efficiency program. C H A P T E R 2 Application of Freight Emissions

2.1.2 State Climate Action Plans Many states have estimated GHG emissions from freight transportation as part of state climate change action plans. More than 30 states have developed climate plans. This process typically starts with the development of a GHG inventory and forecast for the state, using methods laid out in EPA’s State Greenhouse Gas Inventory Tool. The inventory and forecast is an essential step in identifying effective GHG mitigation strategies. Following the inventory and forecast, freight emissions are estimated when the benefits and costs of specific GHG mitiga- tion strategies are evaluated. Most state climate action plans include recommendations for one or two freight-focused miti- gation strategies. The most common are truck idle reduction, truck fuel efficiency improvements, and freight mode shift to more fuel efficient modes. Like the EPA GHG Inventory, state climate plans estimate the six primary GHGs identified by the IPCC, and include three of these gases for freight sources: CO2, N2O, and CH4. Emissions of the three gases are combined to be reported in terms of CO2 equivalent. Exhibit 2-1 shows a typical example of how transportation GHG emissions are presented in a state climate action plan. In most states, the estimate of freight GHG emissions in the state climate action plan does not directly influence public- or private-sector decision making. The state agencies or stake- holder groups that develop recommendations for mitigation strategies may refer to the inventory and forecast as a way to identify those strategies with the largest potential benefit. In reality, however, the selection of mitigation strategies typically is based on which strategies are thought to be feasible and cost effective, not on which sources contribute the most to the state’s emissions. In states that have mandatory GHG reduction require- ments, the emission inventory will be critical for determining compliance with reductions in future years. Approximately 20 states have established GHG reduction targets; to date, only California has mandated an economy-wide emissions cap that includes enforceable penalties. When individual mitigation strategies are analyzed, the estimate of freight emissions reduction is often done in a relatively simplistic manner, given the time and resource constraints on plan development. The estimation of emissions reduction and cost effectiveness could potentially influence a decision by the state to adopt a policy or implement a program. To date, however, there are few examples of state climate action plans leading to the adoption of GHG mitigation strategies focused on the freight sector. Again, California is an exception, implementing or considering several regulations and programs to reduce freight emissions pursuant to AB 32, Global Warming Solutions Act, mandating GHG reductions. (14) These efforts include the following: • Ship electrification at ports (adopted December 2007), • Ocean-going vessel speed reduction (proposed), • Clean ship measure (proposed), • Port drayage truck rule (adopted December 2007), • Commercial harbor craft educational program (proposed), and • Expanded regulations on transport refrigeration units (proposed). In these instances, the estimation of GHG impacts is a key factor in the state’s decision to pursue these measures. 2.1.3 National- and State-Level Health Risk Assessments EPA has sponsored numerous studies of the public health effects of air pollution. Many of these studies begin with esti- 17 0 10 20 30 40 50 60 19 90 19 92 19 94 19 96 19 98 20 00 20 02 20 04 20 06 20 08 20 10 20 12 20 14 20 16 20 18 20 20 G HG E m is si on s, M M TC O 2e Other Rail Boats and Ships-Offshore Boats and Ships- Ports/Inshore Jet Fuel/Av. Gas Exhibit 2-1. Example state transportation GHG emissions by source type, 1990–2020.

mates of emissions, including freight emissions. One of the most influential studies is the National Air Toxics Assessment (NATA). (15) NATA produces screening-level estimates of cancer and non-cancer health effects of air toxics by census tract for the entire United States. NATA studies have been performed for 1996, 1999, and 2002, and work is continuing on studies for 2005 and 2008. As shown in Exhibit 2-2, NATA starts with county-level emissions estimates from the NEI. The NEI includes all emissions sources (point, area, on-road mobile, and nonroad mobile) and is developed by state air quality agencies and EPA for more than 100 air toxics as well as criteria pollutants. It includes emissions from trucks, locomotives, marine vessels, aircraft, and nonroad equipment, although the emissions estimates can be simplistic due to the broad geographic scale. County-level emissions in the NEI are allocated to census tracts using spatial surrogates. Dispersion modeling is used to estimate tract-level pollutant concentrations. For mobile and area sources, dispersion modeling is done using the Assess- ment System for Population Exposure Nationwide (ASPEN) model; for point sources, dispersion modeling is done using the Human Exposure Model (HEM). (Both these models are exposure models that include dispersion modules.) The Hazardous Air Pollutant Exposure Model (HAPEM) is used to estimate exposure, using tract-level data on activity patterns and demographics. Because of its broad scope, NATA is primarily a screening tool, and EPA advises not to use the results by themselves to identify toxics hotspots or pinpoint specific risk values by census tract. EPA uses the results of assessments in a variety of ways, including the following: • Set priorities for improving emission inventories, • Direct priorities in expanding EPA’s air toxics monitoring network, • More effectively target risk reduction activities, • Identify pollutants and industrial source categories of great- est concern, • Help set priorities for the collection of additional informa- tion, and • Improve understanding of the risk from air toxics. Another example of a national-scale health risk assessment is the work that supports the periodic review of the NAAQS. Under the Clean Air Act, EPA is required to periodically review the NAAQS and, if warranted, modify them to protect public health and welfare. The decision to modify the NAAQS is based on epidemiological studies and on exposure modeling. Review of the NAAQS also involves advice from an independent Clean Air Scientific Advisory Committee (CASAC). EPA has recently completed exposure modeling for the NAAQS review for two pollutants, NO2 and SO2. (16–17) The studies focused on a small number of specific geographic locations, including Atlanta and Philadelphia for NO2 review, and several counties in Missouri for SO2 review. Like NATA, the exposure modeling starts with emissions data from the National Emission Inventory, although roadway emissions were estimated using roadway link traffic volumes from regional travel demand models. Dispersion modeling was done using AERMOD, and exposure modeling was done using the Air Pollution Exposure Model (APEX). These studies result in estimates of the number of individuals exposed to different benchmark levels of air pollution, as illustrated in Exhibit 2-3. The results of this exposure modeling supports the NAAQS review process and, in combination with results from epi- demiological studies, could lead to change in the NAAQS, with far-reaching consequences for public agencies and industry in affected regions. 2.2 Regional-Scale Applications Regional-scale application of freight emissions estimates includes the development of state implementation plans (SIPs) and related Transportation Conformity determinations, as well as regional-scale health risk assessments. 2.2.1 SIP Development When measured concentrations of a criteria pollutant within a geographic region are below those allowed by the NAAQS, EPA designates the region as an attainment area for that pollutant; regions where concentrations of criteria pollutants exceed federal standards are called nonattainment areas. Former 18 Emissions by County (NEI) 100+ toxics •Point •Area •On-Road •Non-Road Emissions by Tract Concentrations by Tract Cancer and Non-Cancer Risk by Tract Allocation to tracts ASPEN HEM HAPEMState andEPA data Exhibit 2-2. National air toxics assessment process (simplified).

nonattainment areas that have attained NAAQS are designated as maintenance areas. Each nonattainment area is required to develop and implement a SIP that documents how the region will reach attainment levels within periods specified in the Clean Air Act. The SIP typically includes (1) a discussion of the region’s air quality issues, (2) a demonstration (using regional dispersion and photochemical modeling) of the emission reductions that are needed to decrease concentrations of the nonattainment pollutants to below the NAAQS, (3) a discussion of the regu- lations or programs proposed (usually by the state air quality agency for the area) to achieve the necessary emissions reduc- tions, (4) an analysis of the emissions impacts of the selected set of regulations or programs, and (5) evidence of federally enforceable commitments the agency has made to imple- ment the proposed regulations or programs. The attainment demonstration establishes the target emissions level—the “emissions budget”—that the area must achieve in order to attain the NAAQS. The SIP inventory estimates primary emissions (those produced directly by a source) of the nonattainment pollutant. The SIP modeling estimates secondary emissions (those pro- duced by chemical reactions of precursor pollutants in the atmosphere). Thus, the inventory must also include emissions of any precursors to the nonattainment pollutant, and the modeling includes their atmospheric reactions that produce the nonattainment pollutant. The regional emissions inventory is a critical element of the SIP process because all modeling of concentrations depends on knowledge of the emissions in the nonattainment area (and sometimes the emissions upwind of the area as well). The regional emissions inventory is forecast to future years and compared to the emissions budget in order to track the area’s progress over time toward attainment. The emission inventory identifies the contribution of each source type to the area’s total emissions. The emission inventory informs the air quality agency’s planning process for developing, evaluating, and selecting emission reduction strategies. Emission inventory information also helps the agency allocate resources most efficiently to produce the greatest emissions reductions at the lowest cost. Some attainment areas or regions within attainment areas voluntarily develop emission inventories for planning purposes. These purposes may include voluntary emission reduction initiatives and development of emission reduction strategies in areas that anticipate becoming nonattainment areas in the near future. Regional emission inventories follow the EPA classification scheme that divides emission sources into point, area, and mobile categories. Point sources are stationary sources that have a stack or other definable location from which emissions emanate (e.g., fossil-fueled electric power plant). Calculation of the point source emissions inventory is relatively straight- forward because characteristics of many sources are obtain- 19 Source: Risk and Exposure Assessment to Support the Review of the NO2 Primary National Ambient Air Quality Standard, EPA-452/R-08-008a (Washington, D.C.: EPA, November 2008), p. 199. Exhibit 2-3. Example of estimated number of asthmatic children with at least one NO2 exposure at or above health effect benchmark levels.

able from their required air quality permits. Area sources are generally point sources that are too small to inventory indi- vidually, such as small dry cleaning establishments. Area source emissions are estimated using economic and demographic information where source-specific data are unavailable. Mobile sources usually are divided into on-road and off-road compo- nents for inventory purposes. On-road mobile sources consist of cars, trucks, motorcycles, and buses. Off-road mobile sources consist of several diverse groups such as construction equip- ment, railroad locomotives, ships and boats, port cargo handling equipment, aircraft, and aircraft ground support equipment. Accordingly, in a regional emissions inventory, the sources of freight-related emissions are classified almost exclusively as on-road and off-road mobile sources. Since passage of the Clean Air Act Amendments (CAAA), EPA has tightened its emission standards considerably on nearly all source categories. Many nonroad sources are subject to retrofit requirements reducing emissions at the time of overhaul. This reduces emissions better than regulation that only addresses freshly manufactured equipment. Until recent years, the nonroad mobile source category was a relative exception. As emission control requirements on other sources, including highway vehicles, have become stricter, their relative shares of the total emissions inventory have shrunk. As a result, the off-road mobile source category, which had been less heavily regulated and includes many engines with long life- times and consequent slow rates of replacement with cleaner models, contributes an increasing share of the total emissions. In recent years EPA, state air quality agencies, and port/airport operators have focused greater regulatory attention on off-road mobile sources. This has included adoption of retrofit require- ments for in-use (as opposed to new) equipment. Because a large proportion of off-road mobile sources are associated with freight transport, the importance of freight-related emission calculations for the off-road components of regional emission inventories is increasing. 2.2.2 Transportation Conformity Section 176(c) of the Clean Air Act (CAA) prohibits federal agencies from taking actions in nonattainment or maintenance areas that do not “conform” to the area’s SIP. The purpose of this conformity requirement is to ensure that general activ- ities do not interfere with meeting the emissions targets in the SIPs, do not cause or contribute to new violations of the NAAQS, and do not impede the ability to attain or maintain the NAAQS. The conformity rules apply only to criteria pollutants. The EPA has issued two sets of regulations to implement CAA Section 176(c), as follow: • Transportation Conformity Rules (40 CFR 51, Subpart T), which apply to transportation plans, programs, and projects funded under Title 23, U.S. Code, or the Federal Transit Act. Highway and transit infrastructure projects funded by FHWA or the Federal Transit Administration (FTA) usually are subject to transportation conformity. A region’s FHWA- required long-range transportation plan also is subject to Transportation Conformity. • General Conformity Rules (40 CFR 51, Subpart W) apply to all other federal actions not covered under Transportation Conformity. The General Conformity Rules established emissions thresholds, or de minimis levels, for use in eval- uating the conformity of an action. General Conformity typically applies at the project-scale for airports, seaports, and military bases. In metropolitan regions within nonattainment areas, the federally designated metropolitan planning organization prepares the FHWA-required long-range transportation plan, which is subject to Transportation Conformity, as previously noted. The conformity demonstration for the plan is based on an emissions inventory for the highway system in the region subject to the plan. This inventory usually is coordinated with, or is a subset of, the nonattainment area’s regional mobile source emissions inventory. Exhibits 2-4 and 2-5 present example emissions tables from a regional conformity determination for a long-range transportation plan. Freight trucks are included in the traffic data (counted or projected traffic volumes by road segment) that are input to the travel modeling that supports the plan’s inventory cal- culations. Although diesel-fueled trucks are relatively high emitters of NOX and PM2.5 on a per vehicle basis, the emission 20 VOC Emissions (Tons per Summer Day) Year Region Action Emissions Statewide Action Emissions Emissions Budget Difference (Action – Budget) 2000 n/a 166.5 n/a n/a 2007 22.7 62.0 86.7 -24.7 2010 18.7 49.7 86.7 -37.0 2020 13.5 29.8 86.7 -56.9 2030 12.9 28.7 86.7 -58.0 Exhibit 2-4. Example of VOC emissions tables from a regional conformity determination for a long-range transportation plan.

inventories for most Transportation Conformity demonstra- tions do not analyze trucks as a separate source category because truck volumes are a relatively small fraction of total traffic volumes and most long-range transportation plans contain few dedicated freight facilities. In contrast, where a nonattain- ment area is considering truck-oriented strategies to reduce emissions, the mobile source inventory for the area’s SIP may address heavy-duty diesel trucks in greater detail, especially in PM2.5 nonattainment areas. 2.2.3 Regional Health Risk Assessments Freight emissions figure prominently in many health risk assessments because freight transportation is a major source of diesel PM in many areas. A number of regions have prepared health risk assessments to better understand the relationship between emissions and public health at the metropolitan scale. Major studies include the following: • Multiple Air Toxics Exposure Study III (MATES III) in the Los Angeles metropolitan area is led by the South Coast Air Quality Management District. (18) • Puget Sound Air Toxics Evaluation, led by the Puget Sound Clean Air Agency in conjunction with Washington State Department of Ecology. (19) • Portland Air Toxics Assessment (PATA), led by the Oregon Department of Environmental Quality with Portland METRO and EPA. (20) • Houston Exposure to Air Toxics Study (HEATS) is a collab- orative study involving local universities, state, federal, and local government agencies, and research organizations. (21) These studies typically begin with a detailed inventory of air emissions, including the six priority mobile source air toxics (MSATs) defined by EPA as acetaldehyde, acrolein, benzene, 1,3-butadiene, diesel particulate matter, and formaldehyde. (22) Air quality modeling is then used to estimate resultant average pollutant concentrations throughout the region. Several different air quality modeling tools have been used for these studies, including CAMx (for MATES III) and CALPUFF (for PATA). Ambient air pollution monitoring data are typically compared to modeled concentrations in order to assess the accuracy of the model. The health risk assessments then use exposure models to link ambient concentrations of pollutants with population, activity, and other parameters to determine overall population exposure. An exposure model attempts to characterize the activities and movement of individuals within a given area, usually a census area, and from that estimate a range of con- centrations to which that population would be subject. For example, in a given census tract there are young children and the elderly who remain indoors most hours of the day, older children who go to school or play outdoors, workers who commute to other areas, and others with a range of activities. Varying ranges of activities expose individuals to different amounts of outdoor ambient air, or outdoor air as it infiltrates buildings. An exposure model uses information from each census tract to estimate the range in age of the population, their activities, and commuting habits, and calculates a range of concentrations to which they are exposed. (20) Toxicity factors for each pollutant are combined with expo- sure estimates to estimate health risk—the probability of an adverse health outcome. Risk can then be illustrated on a map as shown in Exhibit 2-6. In most of these studies, diesel particulate matter is the dom- inant source of cancer risk. For example, the MATES III study found that the cancer risk from air toxics in the Los Angeles region is about 1,200 per million, and about 84% of that risk comes from diesel exhaust. In many cases, freight transport is the largest source of diesel emissions. Regional health risk assessments are used by regional, state, and federal agencies to develop more effective strategies to reduce risks to residents. In places like the Portland and Seattle regions, which are in attainment for PM and ozone, the studies have been used to support planning and investments in diesel emission reduction programs. Although these areas do not violate federal air quality standards, they are still interested in reducing the negative health impacts of air toxics emissions. For example, the PATA study is described as a “key step in a community planning process to reduce air toxics in the Portland area.” (23) 21 NOx Emissions (Tons per Summer Day) Year Region Action Emissions Statewide Action Emissions Emissions Budget Difference (Action – Budget) 2000 n/a 287.9 n/a n/a 2007 63.8 174.1 226.4 -52.3 2010 48.3 129.2 226.4 -97.2 2020 24.3 45.4 226.4 -180.9 2030 20.2 34.7 226.4 -191.6 Exhibit 2-5. Example of NOX emissions tables from a regional conformity determination for a long-range transportation plan.

2.3 Project-Scale Applications At the project scale, freight emissions estimates can directly affect the go/no-go decision for a project, or can influence decisions to invest in mitigation measures. Project-scale applications include the comparison among project alternatives and assessment of air quality compliance as required by NEPA and similar state statutes. They can include project-scale emis- sions estimates to satisfy the Conformity Regulations. They also can include emissions estimates for discrete freight facilities and terminals, including railyards, seaports, and airports. 2.3.1 NEPA and Similar State Processes Requirements NEPA is the foundation of environmental impact analyses in the United States and usually provides the forum in which project-level emission estimates are made and air quality impacts evaluated. Under NEPA, a project must be assessed if it involves a “major federal action significantly affecting the quality of the human environment.” (24) Every project must be evaluated to determine whether it meets this threshold. Some federal agencies maintain lists of Categorical Exclusions (CEs) that specify project types that the agency presumes will not have a significant impact. Normally, CEs do not require detailed emissions analysis. Projects that could have a signifi- cant impact require either an environmental assessment (EA) if the agency believes the potential for significant impacts is low or an environmental impact statement (EIS) if the agency believes the potential for significant impacts is high. The methods for estimating freight emissions are essentially the same for EA and EIS, although the level of detail may be greater for an EIS. Most large transportation infrastructure projects—whether or not dedicated to freight—fall under NEPA because they entail funding, permitting, or other approval by a federal 22 Source: Multiple Air Toxics Exposure Study III (MATES III), South Coast Air Quality Management District at http://www.aqmd.gov/prdas/matesIII/matesIII.html. Exhibit 2-6. Example of regional-scale model estimate of cancer risk.

agency. For many projects, the application of NEPA is clear because federal jurisdiction occurs directly, often with several agencies and actions. For example, a new interstate highway would carry truck traffic and might involve FHWA funding, consultation on endangered species with the U.S. Fish and Wildlife Service, and wetlands permits from the Army Corps of Engineers, among others. For other freight projects, the event that triggers NEPA may not be obvious; for example, a state DOT that is sponsoring a truck stop project may support part of the project from FHWA grant funds. An airport may construct a cargo facility that would not require federal involve- ment but the project appears on the Airport Layout Plan, and a change to the Airport Layout Plan requires approval by the FAA. From the NEPA perspective, most transportation infrastructure projects involve emissions from multiple vehicles or sources, only a portion of which happen to be hauling freight. Emissions analyses under NEPA treat freight-related emissions in greater or lesser detail depending on the magnitude and significance of emissions from the freight-related activities that would be served by, or affected by, the project. The level of rigor and detail for the freight emissions analysis is largely a project-specific decision. Freight railroad projects may trigger NEPA due to fund- ing by FRA or permitting by other federal agencies as in the highway example above. Freight railroad projects that con- sist only of operational changes rather than infrastructure construction also may trigger NEPA if they fall under the jurisdiction of the federal Surface Transportation Board (STB). Several types of economic actions, including certain railroad mergers, acquisitions, and proposals for new services over existing railroad lines, require STB approval and consequent NEPA review. Several states, including Washington, Massachusetts, and California, have statutes similar to NEPA that establish state- level environmental review processes. The state-level review processes have various triggers that differ from state to state. Triggers include type of project, size of project, cost of project, requirement for a state agency permit, and use of state funds. Some state processes mandate preparation of NEPA-like documents that cover impacts to all resource areas (air quality, water quality, etc.), while other processes may include only the subject matter of the triggering event (e.g., a project that must obtain an access permit for an entrance that fronts a state highway might be required only to analyze traffic impacts). Projects located in California are subject to the California Environmental Quality Act (CEQA) process. Unlike most state processes, CEQA and its implementation by California’s air quality management districts (sub-state regional agencies to which California has delegated some air quality regulatory authority) often necessitate more complex air quality analysis and more mitigation effort than NEPA does. In many cases, the state-level review proceeds concurrently with NEPA, and the lead agency produces a single environmental impact document that satisfies both NEPA and the state review process. A few municipalities have their own environmental review processes that are similar to NEPA and may require similar air quality analysis. Types of Emissions Estimated under NEPA Project-level emissions analyses under NEPA and similar state laws focus primarily on the criteria pollutants. However, as concern about MSATs has mounted, FHWA and state DOTs have increasingly received requests for MSAT analysis in agency-funded EISs. The issue of air toxics has been raised with several major highway projects around the country, resulting in lengthy deliberations and, in some cases, litigation. (25–26) At the same time, the FAA has also received increasing requests for MSAT analysis in its EISs for airport projects. Airport projects typically involve MSAT emissions from multiple source classes including aircraft, on-road vehicles, and off-road sources such as aircraft ground support equipment (GSE) and construction equipment. Experience in the early 2000s with MSAT analysis for major EISs at large airports such as Los Angeles International, (27) Chicago O’Hare (28) and Philadelphia International (29) led to FAA’s issuance of interim MSAT guidance. (30) California agencies have long required MSAT analysis as well as health risk assessment in CEQA environmental impact reports (EIRs), which are the California state-level counterpart to NEPA EISs. Most projects focus on priority MSATs because they represent the bulk of total health risk. The MATES III study identifies DPM as the primary cancer risk factor out of all MSATs. Proximity to transportation facilities, typically roadways, has been estab- lished as a primary factor leading to community exposure and potentially increased risk. HAPs other than MSATs are normally not evaluated sepa- rately in NEPA analyses of transportation projects. MSATs as a class, and priority MSATs in particular, should be good surrogates for all relevant HAPs because most are species of VOC or PM. The speciation distributions of VOC emis- sions are generally similar for broad classes of transportation sources. The speciation of PM emissions differs markedly between gasoline and diesel sources, but less so within the diesel source classes. In most cases, if emissions of priority MSATs are insignificant, then emissions of other transporta- tion HAPs also will be insignificant and need not be analyzed in detail. Requests during NEPA, CEQA, and state-level scoping to include GHG emissions have become commonplace and many agencies now routinely require these GHGs in project emission estimates. The White House Council on Environmental Quality (CEQ) issued draft NEPA guidance on climate change in 1997 that was never finalized. (31) 23

NEPA Application: Comparison of Proposed Project Alternatives Emissions estimates are used for purposes of disclosure and agency decision making. NEPA requires that project impacts be disclosed to the public and that the sponsoring agency make a determination as to whether the impacts of the proj- ect would be “significant.” Potentially, the most important use of emission estimates is to assist the agency in selecting which alternative to implement from the set of project alter- natives. In NEPA and similar processes, the alternative selec- tion must consider air quality impacts as well as impacts on other resource areas. For purposes of alternative selection, the absolute magnitude of a project’s air quality impact may be less important than the relative differences or ranking of air quality impacts among the alternatives and the directional trend in predicted emissions over time. Air quality impacts are characterized by emissions for overall or regional-level comparisons among alternatives and for purposes of compliance with the EPA Transportation Conformity and General Conformity Rules. Where localized impacts are a concern, emissions data are used for input to dispersion modeling that estimates the pollutant concentra- tions at specific locations for comparison to the NAAQS and state standards for criteria pollutants. NAAQS have not been established for MSATs, although some states have established guidelines for ambient MSAT concentrations. If significant MSAT impacts are anticipated, the dispersion model results may be used as input to a human health risk assessment. Most project-related health risk assessments are conducted in California under CEQA and agency processes for air quality permitting of stationary emission sources. No ambient standards exist for GHGs. Most analyses report GHG emissions by project alternative and may provide a simple comparison of project GHG emissions to the total GHG emissions in the region or state. Climate change impacts of GHGs usually are treated as a cumulative impact under NEPA. Currently, the state of the practice for project-level GHG/ climate change analysis is evolving. For many projects, especially highways, the emissions from project alternatives may differ very little in relative terms. For such projects, the influence of emissions on agency decisions tends to be slight at most. This is true for both highway projects in general and also for the portion of emissions from freight trucks, since most highway projects do not involve dedicated truck facilities that would necessitate a separate accounting of truck emissions. However, if the geographic variation of the project alternatives is large (multiple corridors or diverse communities), then the equity considerations of where the impacts would occur may loom larger in agency review and public comment than considerations of the mag- nitude of emissions. These concerns often are addressed in 24 the socioeconomic and environmental justice sections of an EA/EIS, and therefore the air quality analysis would be suffi- ciently detailed to support evaluation of these resource areas. Highway impacts of MSATs and PM are related mostly to heavy-duty diesel trucks and, as a result, the freight compo- nent of the project emissions must be accounted for in these analyses. Railroad projects may be entirely freight-related or may include passenger train movements and possibly effects on highway traffic volumes due to project-induced changes in modal shares. Port projects are usually dominated by freight movement and involve emissions mostly from diesel engine sources. For these projects, almost all of the project impact comes from freight. Airport emissions usually are dominated by emissions from passenger aircraft and GSE, followed by motor vehicles accessing the airport. Air freight may be carried in dedicated cargo aircraft, which are a small proportion of the total flights at most airports, as well as “belly cargo” in passenger aircraft. For these reasons, the emissions due to freight as opposed to passenger operations at an airport can be difficult to separate within the total aircraft and GSE emissions. The results of emissions calculations may be presented in various ways depending on the project and the intended audience. Exhibit 2-7 presents an example of a table showing the emissions estimate for a single project alternative at an airport. Exhibit 2-8 presents an example of an EIS emissions comparison among all alternatives for a highway project. NEPA Application: Ambient Air Quality Standards Compliance and Health Risk Assessment Local air quality impacts in the project vicinity are evaluated using dispersion modeling that produces estimated pollutant concentrations at specific locations of interest (known as receptors). Typical receptors include residences, health care facilities, educational facilities, and recreational areas. The estimated concentrations are compared to the NAAQS and other applicable standards to determine compliance and the significance of the impacts. Dispersion modeling typically is conducted as part of project analysis under NEPA and similar state review processes, but also may be performed for project- level Transportation Conformity evaluations, applications for funding or air quality permits, and planning studies. Because concentrations are being compared to numerical standards, the absolute levels of impact must be calculated and it is important to choose calculation methods that yield the greatest possible confidence in the numerical results. The decision on whether to model the ambient pollutant concentrations or health risks due to a project is based on an assessment of whether the project’s impacts are likely to be significant. Under NEPA, the threshold of significance for concentrations is commonly taken to be the NAAQS. Under

NEPA and similar review processes, public or agency comments during project scoping may indicate sufficient concern to per- form modeling even if impacts are expected to be insignificant. Some agencies have issued quantitative guidelines based on traffic volumes, aircraft operations, proximity to receptors, or similar criteria that determine whether dispersion modeling should be conducted for a project. At other agencies, the decision may be based on professional judgment informed by precedent, the results of previous projects, or the current state of modeling practice. Similar considerations apply to a decision on whether to conduct a health risk assessment for a project. For highway projects and other projects involving highway traffic access (potentially almost any type of freight project), 25 criteria pollutant impacts are modeled at “hotspots,” which are locations at which relatively high emissions are expected to occur due to traffic congestion. Hotspot modeling is used to assess impacts of CO, PM, and sometimes NOX. Typical hotspot types include signalized intersections, roadway/rail grade crossings, and other locations where queuing occurs such as toll plazas and freight terminal entrances. Most agency guidance specifies use of the EPA CAL3QHC model, or the California DOT (Caltrans) CALINE4 model in California. Prior to dispersion modeling, potential hotspots normally are screened according to traffic volumes, level of service, and queuing levels with the worst locations being selected for air quality modeling. In the past, criteria pollutant impacts also Projected Emissions (kg/Day) Source Categories VOCs NOx CO Aircraft Sources1 Air carriers 350 4,300 3,337 Commuter aircraft 61 459 640 Cargo aircraft 21 309 194 General aviation 304 61 499 Total aircraft sources 736 5,129 4,669 Ground Service Equipment2 234 294 5,670 Motor Vehicles Parking/curbside 16 5 112 On-airport vehicles 60 79 851 Total motor vehicle sources 76 84 963 Other Sources3 Fuel storage/handling 475 0 0 Miscellaneous sources 9 211 33 Total other sources 484 211 33 Total airport sources 1,530 5,717 11,335 Notes: 1 Calculations for 2020 are based on taxi times based on the proposed Airport Improvements Planning Project. 2 Includes vehicles and equipment converted to alternative fuels based on the 2004 fleet mix. 3 Includes the central heating and cooling plant, emergency electricity generation, and other stationary sources. Exhibit 2-7. Example emissions estimate for a single alternative for an airport project. 2008 2012 Pollutant Existing Conditions No-Build Alternative Build Alternative 1 Build Alternative 2 Build Alternative 3 CO 74.92 76.02 82.49 78.56 79.63 VOC 2.77 2.88 3.28 3.04 3.10 NOX 1.61 2.17 2.48 2.29 2.34 SO2 0.14 0.19 0.20 0.19 0.20 PM10 4.25 4.37 4.61 4.42 4.49 PM2.5 4.01 4.03 4.12 4.04 4.06 Exhibit 2-8. Example EIS emissions comparison among alternatives for a highway project (tons/year).

were modeled at receptors along the highway itself. Emission rates from motor vehicles have decreased steadily due to EPA regulations under the CAAA and now are so low that, in most cases, agencies no longer require dispersion modeling for locations along the highway mainline if vehicles are traveling at cruise speeds. For non-highway projects, projectwide dispersion modeling for criteria pollutants is common, and the criteria pollutant of greatest concern usually is PM. For large projects, and where specified by agency guidance (primarily in California), disper- sion modeling of MSATs is used to characterize concentrations and (again, primarily in California) to support health risk assessments. The MSAT of greatest concern usually is DPM. Although the PM classes PM2.5, PM10, and DPM have unique definitions, in practice their emission rates for freight projects are similar in terms of mass emitted, because for most freight projects the primary emissions source is diesel engines and most DPM falls into the PM2.5 size class. The most commonly specified models for this application are EPA’s AERMOD and CALPUFF. In California, the Hotspots Analysis and Reporting Program (HARP) model combines dispersion modeling and health risk assessment processes. The dispersion component of HARP uses the EPA’s ISC3 model, which is the predecessor of AERMOD. 2.3.2 Project-Level Conformity As discussed in Section 2.2, the conformity regulations prevent federal actions in nonattainment or maintenance areas that interfere with meeting the emissions targets in the SIPs or contribute to new violations of the NAAQS. Most highway projects are included in a conforming regional transportation plan or TIP and thus are subject to Transporta- tion Conformity (Section 2.2.2) as part of the entire plan. In a few limited circumstances, a project that is located in a nonattainment or maintenance area and is subject to Trans- portation Conformity must perform a project-level conformity determination. The project-level conformity determination can entail emissions estimates, air quality modeling studies, consul- tation with EPA and state air quality agencies, and commit- ments to revise the SIP or to implement measures to mitigate air quality impacts. This requirement creates an incentive for agencies to have a project included in the long-range trans- portation plan in order to avoid the need for a project-level conformity evaluation. In many cases, and almost universally with large highway projects, the project is included in the plan’s travel modeling from the outset. The General Conformity Rules apply to all other federal actions not covered under Transportation Conformity. General Conformity typically applies at the project-scale for airports and seaports. The General Conformity Rules established emis- sions thresholds, or de minimis levels, for use in evaluating the conformity of an action. Because the General Conformity Rules have absolute emissions thresholds for project-related emis- sion increases, it is important to estimate emissions accurately without excessive conservatism (overestimates) and to include design and operational features that will help reduce emission increases below the thresholds and avoid the need for a con- formity determination. If the net emission increases due to the project are less than these thresholds, then the project is presumed to conform and no further conformity evaluation is required. If the emission increases exceed any of these thresholds, then a conformity determination is required. The conformity determination can entail air quality modeling studies, consultation with EPA and state air quality agencies, and commitments to revise the SIP or to implement measures to mitigate air quality impacts. The conformity process is separate from NEPA and other environmental reviews but, because the required technical studies are very similar, a conformity evaluation usually is conducted concurrently with other environmental review processes. 2.3.3 Emissions Estimates for Linear Projects Transportation infrastructure projects that are linear in nature include highways, rail lines, and some waterways. These projects may span multiple state and local jurisdictions, and federal involvement is almost assured. Emissions estimates are required for NEPA, sometimes for conformity, and to support dispersion modeling of project impacts. In California, they may support health risk assessments as well. Project-level emission estimates for linear transportation projects generally are used only for project approval, and are not used directly in regional emission inventories or SIPs. Exhibit 2-9 presents typical characteristics of emission inventories for linear freight transportation projects. Emissions are estimated separately by type of source. 2.3.4 Emissions Estimates for Discrete Freight Facilities/Terminals Railyard Health Risk Assessments Locomotive emissions estimates have been used to prepare health risk assessments (HRAs) for major railyards in California. BNSF and UP agreed to prepare these HRAs for 17 individ- ual railyards when they signed a statewide railroad pollution reduction agreement with CARB in 2005. The HRAs must be prepared based on CARB’s experience in preparing the Roseville Railyard Study (32) as well as CARB guidance. (33) Emissions are estimated for all sources within the railyards, potentially including locomotives, on-road trucks, cargo han- dling equipment, heavy equipment, transport refrigeration 26

units (TRUs) and refrigerated rail cars, stationary sources, and portable equipment. These emission inventories, conducted by the railroads and CARB, focus on emissions of TACs— primarily diesel PM, but also gasoline TACs such as isopentane, toluene, and benzene. The studies start with preparation of an emission inventory, which is performed by the railroads following CARB guidance. (34) Emissions are reported by source type, as illustrated in Exhibit 2-10. The railroads then estimated pollutant concentrations in the vicinity of the railyard using AERMOD, an EPA-approved dispersion model. In addition to the emissions, meteorological factors (including wind speed and wind direction) are key inputs to the dispersion model. CARB multiplied the resulting concentrations by cancer risk factors to estimate cancer risk, expressed as the chances of excess cancer risk per million people. Cancer risk is illustrated using isopleths—lines drawn on a map through all points of equal cancer risk. Exhibit 2-11 shows an example of this presentation. These railyard health risk assessments are prepared under voluntary agreements and are not directly related to any reg- ulation or government decision-making process. However, 27 Project Type Regulatory Process and Use of Emissions Estimates* Major Features of Emissions Estimates NEPA State Env. Review Transp. Conf.** General Conf.** Planning/ Initiatives Typical Sources Included Construction Emissions Emissions Models Used Linear Project Highway (in some states) – Trucks, Cars No MOBILE6.2, MOVES (draft), EMFAC (in CA) Railroad (in some states) – – Locomotives, Trucks (Freight Diversion) For General Conformity only MOBILE6.2, MOVES (draft), EMFAC (in CA), off-model databases and calculations Waterborne (e.g., Canals, Channel Dredging) (in some states) – – Ships, Dredges, Support Vessels For General Conformity only Off-model databases and calculations Discrete Facility Truck Stop or Terminal S S S – S S Trucks For General Conformity only MOBILE6.2, MOVES (draft), EMFAC (in CA) Railyard or Intermodal Terminal S S Locomotives, Trucks (Drayage), Cargo Handling Equipment No MOBILE6.2, MOVES (draft), EMFAC (in CA), NONROAD, OFFROAD (in CA) Seaport (in some states) – Ocean-Going Vessels, Harbor Craft, Cargo Handling Equipment, Locomotives, Trucks (Drayage), Stationary Sources, Electric Power Generation For General Conformity only MOBILE6.2, MOVES (draft), EMFAC (in CA), NONROAD, OFFROAD (in CA), off-model databases and calculations Airport (in some states) S S Aircraft, GSE, Trucks, Cars, Buses/Vans, Fuel Handling, Stationary Sources, Electric Power Generation For General Conformity only EDMS, off-model databases and calculations Notes: * Process: Likely; – Unlikely; S Sometimes, depending on project size and federal involvement. ** Conformity rules apply in nonattainment and maintenance areas only. Exhibit 2-9. Typical characteristics of emission inventories for freight transportation projects. On-Site Sources Railyard 1 Railyard 2 Railyard 3 Railyard 4 Total % of Total Locomotives 4.9 5.9 2.3 0.6 13.6 33% On-Road Trucks 2.0 10.1 - 1.1 13.2 32% CHE 4.8 4.2 - 0.4 9.4 22% Others 0.4 3.7 0.4 1.0 5.5 13% Total 12.1 23.9 2.7 3.1 41.7 % of Total 29% 57% 7% 7% 100% Exhibit 2-10. Example of railyard diesel PM emissions (tons/year).

HRA reports can influence public policy decisions in a number of ways. The cancer risk estimates provide compelling infor- mation to community and environmental groups advocating for emission controls. CARB uses this information to make decisions regarding new initiatives to reduce diesel emissions. Seaport Emission Inventories Seaports and airports have a number of similarities in activities and institutional settings that affect the estimation of emissions as well as the uses of the emissions inventory. Both seaports and airports are characterized by intermodality: passengers and goods are transported overland to the facility and then transferred to the vehicle (aircraft or ship) for the longer distance portion of the trip. Most of the mass emissions of pollutants of greatest concern for freight (NOX, PM, GHGs) occur en route from the aircraft or ship rather than from the facility. However, the emissions from the ground access trip may be of greatest concern for NAAQS compliance and health risk because of proximity of receptors to roadways and rail lines. Seaport or airport operators may be state agencies, public authorities, municipal departments, or private firms, and, as such, have varying degrees of legal authority and financial capability to address emissions. Private carriers (airlines, shipping lines) operate in public airspace or unmanaged international waters and are largely exempt from regulation by the seaport or airport operators. Efforts by local seaport or airport operators to regulate emissions are constrained by preemption of authority by the federal government or inter- national agreements, and by the need to stay competitive with other ports. (35) Seaport or airport operators do, however, have authority to regulate the types of ground vehicles that may access the facility and vehicle operations while within the facility. Like other projects, seaports and airport projects use project emissions estimates for purposes of NEPA and state-level review, public information, and conformity. In addition, seaports and airports may develop emission inventories for their entire facility. An emission inventory is necessary for port authorities, those doing business at ports (such as terminal operators, tenants, and shipping companies), state and local entities, or other interested parties to understand and quantify the air quality impacts of current port operations and to assess the impacts of port expansion projects or growth in port activity. Because of the wide variety of vehicles and equip- ment that operate in or near their facilities, seaport and airport operators may use emissions estimates to identify emission sources, quantify their contribution to facility-related emis- sions, and evaluate potential emission reduction strategies. The inventory can then be used to develop strategies to mini- mize current and projected emissions and to quantify progress. A facility emissions inventory can inform compliance with 28 Source: Air Resources Board, Health Risk Assessment for the Union Pacific Railroad Commerce Railyard, November 2, 2007. Available at http://www.arb.ca.gov/railyard/hra/up_com_hra.pdf. Exhibit 2-11. Example of estimated potential cancer risks from railyards (chances per million people).

regulatory requirements such as those in SIPs for criteria pollutants or city/state climate action plans for GHGs, and also inform voluntary initiatives such as a collaborative regional MSAT assessment or development of a seaport/airport environ- mental management system. (36) Exhibit 2-12 presents an example summary of a facility emissions inventory prepared by a large seaport. Airport Emission Inventories As noted previously, seaports and airports share many operational and institutional similarities. Airports prepare emission inventories for the same reasons that seaports do. The emission inventories play equivalent roles in airport decision making. Airport-related emissions from each type of source are calculated in the same way as for seaports, with the exception that aircraft emissions replace vessel emissions, and GSE emissions replace CHE emissions. In addition, airports typically have large fuel storage and handling operations with associated emissions from pumps, vehicles, and fuel evapora- tion. Exhibit 2-7 (presented previously) shows an example of a facility emissions inventory prepared by a large airport. FAA guidance specifies that airport-related emissions of criteria pollutants and MSATs from most sources should be calculated using the FAA’s Emissions and Dispersion Modeling System (EDMS). EDMS takes as inputs the same data for each individual source type as previously discussed for highway and rail projects and port facilities. EDMS calculates emissions from airborne aircraft only up to an altitude of approximately 3,000 ft, which corresponds with the average height of the atmospheric mixing layer. Emissions above this altitude gen- erally do not disperse downward to altitudes below the mixing height and accordingly have little or no influence on ground- level air quality. FAA is currently developing a new model, the Aviation Environmental Design Tool, which is planned to eventually replace EDMS. To date, agencies are only beginning to issue guidance on how to estimate GHG emissions associated with airports. A number of methods and assumptions have been used. The current version (5.1) of EDMS estimates CO2, but not other GHG emissions, for aircraft only. A recent attempt to com- pile best practices is ACRP Report 11: Guidebook on Prepar- ing Airport Greenhouse Gas Emissions Inventories. (37) One assumption that can have a very large effect on the results of the emissions calculations is the allocation of aircraft en route emissions—to the departure airport, the arrival airport, or some combination—because these usually are the major portion of aviation-related emissions. 29 Category PM10 PM2.5 DPM NOX SOX CO TOG Ocean-Going Vessels 733 586 637 6,926 6,501 603 274 Harbor Craft 30 27 30 1,004 5 237 20 Cargo Handling Equipment 56 51 56 1,737 17 450 101 Locomotives 43 40 43 1,314 76 183 74 Heavy-Duty Vehicles 243 224 243 5,607 39 1,944 433 Total 1,105 928 1,008 16,587 6,638 3,416 901 Exhibit 2-12. Example of port emission inventory, 2005 (tons/year).

Next: Chapter 3 - Evaluation of Current Methods »
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TRB’s National Freight Cooperative Research Program (NFCRP) Report 4: Representing Freight in Air Quality and Greenhouse Gas Models explores the current methods used to generate air emissions information from all freight transportation activities and their suitability for purposes such as health and climate risk assessments, prioritization of emission reduction activities, and public education.

The report highlights the state of the practice, and potential gaps, strengths, and limitations of current emissions data estimates and methods. The report also examines a conceptual model that offers a comprehensive representation of freight activity by all transportation modes and relationships between modes.

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