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Suggested Citation:"Summary ." National Academies of Sciences, Engineering, and Medicine. 2013. Environmental Assessment of Air and High-Speed Rail Corridors. Washington, DC: The National Academies Press. doi: 10.17226/22520.
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Suggested Citation:"Summary ." National Academies of Sciences, Engineering, and Medicine. 2013. Environmental Assessment of Air and High-Speed Rail Corridors. Washington, DC: The National Academies Press. doi: 10.17226/22520.
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Suggested Citation:"Summary ." National Academies of Sciences, Engineering, and Medicine. 2013. Environmental Assessment of Air and High-Speed Rail Corridors. Washington, DC: The National Academies Press. doi: 10.17226/22520.
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Suggested Citation:"Summary ." National Academies of Sciences, Engineering, and Medicine. 2013. Environmental Assessment of Air and High-Speed Rail Corridors. Washington, DC: The National Academies Press. doi: 10.17226/22520.
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ENVIRONMENTAL ASSESSMENT OF AIR AND HIGH-SPEED RAIL CORRIDORS There is significant experience and research on the competition of air and high-speed rail (HSR) modes. The existing research covers areas including system structure (vehicle tech- nology, cost, ridership, etc.) and environmental effects. The objective of the Environmental Assessment of Air and High-Speed Rail Corridors synthesis is to bring together research and other findings related to air and HSR environmental assessments and to understand where additional research can improve our ability to assess the environmental outcomes of these two systems. A literature review is the primary tool for collecting data for this synthesis of current practice. The literature revealed that there are two approaches to categorizing air and HSR assess- ments: attributional and consequential. Attributional assessments look backward from some point in time and are used to allocate the environmental effects to passenger travel, a trip, or vehicle travel. Consequential assessments look forward as a result of a system change and can be used to determine the changes to the total regional environmental effects caused by a particular decision. The air and HSR modes, although sometimes overlapping, are structured differently. The aviation system is structured as a system of nodes (i.e., airports) connected with aircraft oper- ated by independent operators. The spatial scale of the nodes is vast, such that passengers can travel between nodes in a region or in two separate countries. Conversely, the HSR system is structured as a system of links, with the spatial scale being limited to a fixed regional area between major cities and the regions between. In contrast, aviation is not planned in corridors. Airports are planned to serve a region, and airlines connect this region to their hub airports and possibly some additional airports. That these two networks may have some overlapping portions yet serve different scales of network presents a complexity when defining the system struc- ture for an environmental assessment. The result is spatial incompatibility between modes; rail service is planned in corridors, whereas air service is planned over a national and global network. Spatial incompatibility across modes makes it difficult to compare environmental assess- ments. Most studies consider air and HSR to be “competitive corridors,” whereas a few view the broader aviation system network and HSR services to be complementary when nearby regions are linked with an airport. The fundamental differences in air and HSR environmental assessments impede the drawing of the analytical system boundary for environmental assess- ments; aviation is a system of nodes with the planning focused on airports, and rail is a series of nodes connected by links with the planning focused on specific corridors. The synthesis focused on two types of literature: government-driven environmental impact assessments and academic. Government-driven environmental impact assessments are in the form of National Environmental Policy Act (NEPA) studies. However, considering the spatial incapability of the two modes, assessing if aviation meets the needs of an HSR project, and vice versa, is a highly complex process. As a result, few detailed modal assessments are found in EIS documents. Those that are present are consequential assessments that focus on a full range of effects to resources consistent with the NEPA process. Government-driven work provides an SUMMARY

2 important framework for assessing air and HSR environmental comparisons, yet the language of NEPA alternatives assessments can preclude a full, detailed analysis of modal alternatives. Although there is a growing body of academic literature that seeks to reconcile spatial incompatibility, the academic literature is not bound by the same legal and institutional pro- tocols of the environmental review process and therefore does not have to draw a constrained system boundary. Academic literature is free to compare any modes, regardless of whether they are implemented, programmed, or conceptual. The following is a sample of results from academic literature: • The substitution of air by HSR was found to reduce NOx, CO, hydrocarbon (HC), and PM10 emissions but increase SOx by a factor of 12 owing to the sulfur content of primary fuels for electricity generation (Givoni 2007). Givoni’s (2007) attributional assessment finds that between Paris and London there were significant reductions in criteria air pol- lutants (CAP) between air and HSR, respectively (18 to 0.4 g/seat HC, 126 to 2.2 g/seat CO, 71 to 18 g/seat NOx, 2.9 to 35 g/seat SOx, and 2.0 to 1.0 g/seat PM10). • A consequential assessment by Jamin et al. in 2004 found that substituting one-third of air travel for HSR in the relevant corridors increases SOx emissions across the corridors from 100 to 2,000 tons and decreases NOx (5,000 to 4,200 tons), HC (2,200 to 1,900 tons), and CO emissions (6,100 to 4,200 tons). This could be important when assessing human health and environmental impacts and would depend on where the emissions occur. Increases in sulfur emissions may result in acidification of soil and groundwater and occur from changes in operation and propulsion energy inputs and life-cycle effects (Chester and Horvath 2012). • In 2002, the European Commission found that people are generally more annoyed by air- craft noise than rail noise, with highway noise falling between these two modes. In 2011, Eagan and Mazur noted that although this certainly has to do with acoustic factors, it also has to do with attitudes toward the noise source. • Along with their spatial incompatibilities, air and HSR can have differing noise profiles. Aircraft noise is primarily a concern for near-airport operations because of the occur- rence of low-altitude flight. Because HSR involves a system of links between stations, HSR noise may or may not occur predominantly at the nodes because of a combination of mitigation possibilities (FRA 2005a), the population density near tracks, and opera- tion characteristics. In general, there is less impact expected near HSR stations than along the route. • Air transport typically requires less land per passenger trip than does HSR transport (Rus 2011). Airport land-take occurs when the airport sees a need for capacity expan- sions, whereas land use impacts from HSR are dependent on the length of HSR line and the environment along the line, not the volume of traffic in the corridor. • Furthermore, it is important that growth-inducing impacts on surrounding land be con- sidered. Both air and HSR systems have the potential to create indirect land use impacts through new residential, commercial, and industrial activities near airports and train stations (Janic 2003). • In 2007, Givoni’s attributional assessment found that between London and Paris the CO2 emissions from HSR travel were 7.2 kg/seat and from air travel 44 kg/seat. • In 2003, Janic’s attributional assessment estimated that the French HSR service (the TGV) emitted 4 g CO2 per passenger-kilometer traveled (89% nuclear electricity), the German HSR service (the ICE) 28 g (50% coal electricity), and a competing flight between 100 and 150 g. These emissions combined with other damages (i.e., other air pollution, noise, land use, congestion, and accidents) are used to monetize the external costs of HSR and air travel, respectively, at Euros 0.002 to 0.01 and 0.02 to 0.08 per passenger-kilometer trav- eled in the United States and Europe. • Chester and Horvath in 2012 included roughly 150 life-cycle components in the assess- ment of future long-distance travel in California and, by first using an attributional approach, found that although HSR is likely to produce lower greenhouse gas (GHG)

3 emissions per passenger-mile traveled, an average occupancy of 130 to 280 passengers is needed to compete with emerging aircraft and one of 80 to 180 passengers to com- pete with a 35-mpg sedan. Chester and Horvath then developed a consequential assess- ment to determine that, given future HSR adoption uncertainty, GHG payback will occur between 20 and 40 years, which includes emissions from construction and maintenance activities. The authors included modeling of emerging technologies, regional flight char- acteristics (instead of multiplying a per seat-mile factor across forecasted seat-miles), and uncertainty in mode shifting. • Givoni (2007) computed the environmental benefits of mode substitution for air and HSR by estimating the aircraft, access/egress, aircraft journey, and HSR journey air pollution externalities per seat between London and Paris. He found that the external costs of travel on HSR are 0.52 Euros per seat and on air are 1.03 Euros. Janic (2003) monetized air emission externalities and estimated that the marginal costs of HSR travel generally are lower than those for air travel in Europe, but Janic did not assess the total costs of each system. In investigating the role of air and HSR as competitors and complementary modes, under- standing ridership is a crucial component. Several studies cite the importance of accurate rid- ership forecasts to understand the environmental outcomes of future long-distance transport systems. Some studies explore the sensitivity of environmental performance to ridership. Other studies focus on understanding the long-run per passenger-mile traveled footprint of passengers to understand the environmental intensity of service. Per-trip measures are com- mon and valuable for eliminating the differences in trip distances to reach the same origin- destination pairs. In an effort to produce unifying analytical boundaries and metrics for comparing air and HSR systems, the following assessments are used in academic literature: life-cycle assessment (LCA), impact assessment, and benefit-cost analysis. LCAs of air and HSR systems can include vehicles (manufacturing and maintenance), infrastructure (construction, operation, and main- tenance), and energy production (primary fuel feedstock extraction, processing, and distribu- tion) components. LCA results for a future California network that includes air and HSR show that (1) for air, life-cycle components can increase the mode’s footprint by roughly 20%, and (2) for HSR, concrete and steel used in infrastructure construction may double the GHG foot- print of the mode. Significant research and efforts have been made by the aviation industry and academics to understand the human health impacts of near-airport operations. Although GHG emission comparisons are critically important, it is also important that future studies consider other pollutants. By defining sustainability and environmental impacts broadly, opportuni- ties will exist for understanding how the (1) reduction in one environmental concern may lead to a reduction in another, or (2) reduction in one environmental concern may lead to an increase in another; that is, an unintended trade-off. Finally, the development of an HSR cost model presents a unique set of challenges compared with the development of an aircraft cost model. Because HSR projects are built over various topographical landscapes, differ- ent technical solutions and levels of investment are needed. Although some studies have attempted to quantify the economic benefits of air travel, similar HSR benefits for a region are not well understood. Various studies in this area range from developing social welfare functions to assess transportation infrastructure investments, to developing a framework to justify HSR projects, to computing the environmental benefits of mode substitution for air and HSR. Through the synthesis of the literature, major gaps in knowledge were found: • Methodological frameworks and tools that assess future operating characteristics of long-distance transportation service have not been fully developed. Such frameworks and tools must address the two main components of the relationship between air and HSR: as competitors and as complementary modes.

4 • A framework and methodology are needed to analyze the impact to airline operations, and thus airport infrastructure use, of development of HSR. The same goes for the “no build” alternative: estimating the future of aviation flows in the absence of HSR infra- structure is necessary. • By performing consequential assessments instead of attributional assessments, orga- nizations will have information about the outcome of decisions that affect air and HSR systems. The consequential assessment will require an understanding of how up-front investments will lead to regional operating effects. Although NEPA in many ways requires a consequential assessment, the academic literature has for the most part avoided these quantifications, likely because of the complexities of accurate estimates. In conclusion, environmental assessments of air and HSR systems have produced valuable knowledge but the creation of novel data analysis and methods will improve our understand- ing of future networks that house both modes. The large body of literature reviewed does not lead to a single cohesive conclusion relating air and HSR comparative environmental analy- sis. By establishing regional planning processes, drawing on previously established methods, and developing new tools and information for better understanding future processes, more comprehensive approaches can be developed to better understand the co-benefits of intel- ligent air and HSR planning.

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TRB’s Airport Cooperative Research Program (ACRP) Synthesis 43: Environmental Assessment of Air and High-Speed Rail Corridors explores where additional research can improve the ability to assess the environmental outcomes of these two systems.

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