Representing Freight in Air Quality and Greenhouse Gas Models (2010) / Chapter Skim
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Pages 16-29
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From page 16... ...
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.
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From page 17... ...
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.
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From page 18... ...
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)
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From page 19... ...
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)
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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 lifetimes and consequent slow rates of replacement with cleaner models, contributes an increasing share of the total emissions.
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Risk can then be illustrated on a map as shown in Exhibit 2-6. In most of these studies, diesel particulate matter is the dominant source of cancer risk.
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Exhibit 2-6. Example of regional-scale model estimate of cancer risk.
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The MATES III study identifies DPM as the primary cancer risk factor out of all MSATs. Proximity to transportation facilities, typically roadways, has been established as a primary factor leading to community exposure and potentially increased risk.
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From page 24... ...
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.
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From page 25... ...
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)
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From page 26... ...
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.
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From page 27... ...
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.
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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.
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From page 29... ...
(36) Exhibit 2-12 presents an example summary of a facility emissions inventory prepared by a large seaport.
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