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Potential Impacts of Climate Change on U.S. Transportation Summary The world’s leading climate scientists have reached consensus that human activity in the form of greenhouse gas (GHG) emissions is warming the planet in ways that will have profound and unsettling impacts on natural resources, energy use, ecosystems, economic activity, and potentially quality of life. The earth’s climate is always in a state of flux, but what is of concern today is the rapid rate of change and the unabated contribution of human activity to its occurrence. Many studies have already examined the potential impacts of climate change on broad sectors of the economy, such as agriculture and forestry, but few have studied the impacts on transportation. The primary focus of this report is on the consequences of climate change1 for the infrastructure and operations of U.S. transportation.2 The report provides transportation professionals with an overview of the scientific consensus on those current and future climate changes of particular relevance to U.S. transportation, including the limitations of present scientific understanding as to their precise timing, magnitude, and geographic location; identifies potential impacts on U.S. transportation and adaptation options; and offers recommendations for both research and actions that can be taken to prepare for climate change. The report also summarizes 1 Climate change refers to a statistically significant variation in either the mean state of the climate or its variability over an extended period, typically decades or longer, that can be attributed to either natural causes or human activity. Weather refers to the familiar hour-by-hour, day-by-day changes in temperature, cloudiness, precipitation, and other atmospheric phenomena. 2 In this report, infrastructure refers to both transportation networks (e.g., road and rail systems) and facilities (e.g., bridges, tunnels, ports). All modes of transportation are covered—highways (including bridges and tunnels), rail (including private rail lines and public transportation), marine and air transportation, and pipelines.
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Potential Impacts of Climate Change on U.S. Transportation previous work on strategies for reducing transportation-related emissions of carbon dioxide (CO2)—the primary GHG—that contribute to climate change, a relatively well-researched area (see Appendix B). Climate change will have significant impacts on transportation, affecting the way U.S. transportation professionals plan, design, construct, operate, and maintain infrastructure. Decisions taken today, particularly those related to the redesign and retrofitting of existing or the location and design of new transportation infrastructure, will affect how well the system adapts to climate change far into the future. Focusing on the problem now should help avoid costly future investments and disruptions to operations. The primary objective of this report is to provide guidance for transportation decision makers on how best to proceed. CLIMATE CHANGES OF GREATEST RELEVANCE FOR U.S. TRANSPORTATION Climate change is not just a problem for the future. Recent global climate changes, such as warming temperatures and rising sea levels, likely reflect the effects of GHG emissions into the atmosphere over the past century. Even if drastic measures were taken today to stabilize or eliminate GHG emissions, the effects of climate change would continue to be experienced, and U.S. transportation professionals would have to adapt to their consequences. On the basis of current knowledge, climate scientists have identified five climate changes of particular importance to transportation and estimated the probability of their occurrence during the 21st century (detailed in Box S-1): Increases in very hot days and heat waves, Increases in Arctic temperatures, Rising sea levels, Increases in intense precipitation events, and Increases in hurricane intensity. Climate scientists have the greatest confidence in projected changes in mean temperature and other climate factors at the global or continental scale; confidence in these projections diminishes as the geographic scale is
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Potential Impacts of Climate Change on U.S. Transportation BOX S-1 Climate Change Impacts of Greatest Relevance for U.S. Transportation Increases in very hot days and heat waves. It is highly likely (greater than 90 percent probability of occurrence) that heat extremes and heat waves will continue to become more intense, longer lasting, and more frequent in most regions during the 21st century. In 2007, for example, the probability of having five summer days at or above 43.3°C (110°F) in Dallas was about 2 percent. In 25 years, this probability increases to 5 percent; in 50 years, to 25 percent; and by 2099, to 90 percent. Increases in Arctic temperatures. Arctic warming is virtually certain (greater than 99 percent probability of occurrence), as temperature increases are expected to be greatest over land and at most high northern latitudes. As much as 90 percent of the upper layer of permafrost could thaw under more pessimistic emission scenarios. The greatest temperature increases in North America are projected to occur in the winter in northern parts of Alaska and Canada as a result of feedback effects of shortened periods of snow cover. By the end of the 21st century, projected warming could range from as much as 10.0°C (18.0°F) in the winter to as little as 2.0°C (3.6°F) in the summer in the northernmost areas. On an annual mean temperature basis for the rest of North America, projected warming ranges from 3.0°C to 5.0°C (5.4°F to 9.0°F), with smaller values near the coasts. Rising sea levels. It is virtually certain (greater than 99 percent probability of occurrence) that sea levels will continue to rise in the 21st century as a result of thermal expansion and loss of mass from ice sheets. The projected global range in sea level rise is from 0.18 m (7.1 in.) to 0.59 m (23.2 in.) by 2099, but the rise will not be geographically uniform. The Atlantic and Gulf Coasts should experience a rise near the global mean, the West Coast a slightly lower rise, and the Arctic Coast a rise of only 0.1 m (3.9 in.). These estimates do not include subsidence in the Gulf and uplift along the New England Coast. Nor do the global projections include the full effects of increased melting of the Greenland and Antarctic ice masses because current understanding of these effects is too limited to permit projection of an upper bound on sea level rise. Increases in intense precipitation events. It is highly likely (greater than 90 percent probability of occurrence) that intense precipitation events will continue to become more frequent in widespread areas of the United States.
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Potential Impacts of Climate Change on U.S. Transportation Increases in hurricane intensity. Increased tropical storm intensities, with larger peak wind speeds and more intense precipitation, are projected as likely (greater than 66 percent probability of occurrence). No robust projections concerning the annual global number of tropical storms have yet emerged from modeling studies, but more detailed analyses focused on the Atlantic Ocean suggest no significant increases in the annual number of Atlantic tropical storms. Note: The primary sources for these data are the 2007 Intergovernmental Panel for Climate Change Summary for Policymakers on the Physical Science Basis (Contribution of Working Group I to the Fourth Assessment Report); the Peterson et al. 2006 paper commissioned for this study (see Appendix C); numerous other sources that can be found in Chapter 2 (see Table 2-1 and the text discussing each of these impacts); and the committee’s own assessments about the certainty of some impacts, based on the literature. reduced. Nevertheless, climate scientists are now able to project climate changes for large subcontinental regions, such as the eastern United States—a scale better suited to transportation infrastructure, which is regional and local. Projections of future climate are often shown as gradual changes, such as the rise in global temperatures projected over this century. However, these changes are unlikely to be experienced in such a smooth manner because those induced by human activity will be amplified in some years by naturally fluctuating conditions, reflected in potentially sudden and dramatic changes at the regional or local level. For example, many climate scientists caution that warming temperatures may trigger weather extremes and surprises, such as more rapid melting of the Arctic sea ice or more rapid rises in sea levels than are projected by current models. Finding: The past several decades of historical regional climate patterns commonly used by transportation planners to guide their operations and investments may no longer be a reliable guide for future plans. In particular, future climate will include new classes (in terms of magnitude and frequency) of weather and climate
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Potential Impacts of Climate Change on U.S. Transportation extremes,3 such as record rainfall and record heat waves, not experienced in modern times as human-induced changes are superimposed on the climate’s natural variability. POTENTIAL IMPACTS ON TRANSPORTATION Transportation professionals are keenly aware of the effects of weather on system performance. Transportation infrastructure was designed for typical weather patterns, reflecting local climate and incorporating assumptions about a reasonable range of temperatures and precipitation levels. Finding: Climate change will affect transportation primarily through increases in several types of weather and climate extremes, such as very hot days; intense precipitation events; intense hurricanes; drought; and rising sea levels, coupled with storm surges and land subsidence. The impacts will vary by mode of transportation and region of the country, but they will be widespread and costly in both human and economic terms and will require significant changes in the planning, design, construction, operation, and maintenance of transportation systems. The infrastructure will be affected most by those climate changes that cause environmental conditions to extend outside the range for which the system was designed (see Table S-1 for illustrative impacts of key climate changes). Finding: Potentially, the greatest impact of climate change for North America’s transportation systems will be flooding of coastal roads, railways, transit systems, and runways because of global rising sea levels, coupled with storm surges and exacerbated in some locations by land subsidence. Fully 53 percent of the U.S. population now lives in counties with coastal regions, many among the most densely populated in the nation. As retirement magnets and tourist destinations with rapidly growing economies, coastal communities will continue to experience development pressures, 3 The exact threshold for what is classified as an extreme varies from one analysis to another, but an extreme event would normally be as rare as or rarer than the top or bottom 10 percent of all occurrences. For the purposes of this report, all tornadoes and hurricanes are considered extreme.
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Potential Impacts of Climate Change on U.S. Transportation TABLE S-1 Potential Climate Changes and Illustrative Impacts on Transportation Potential Climate Change Examples of Impacts on Operations Examples of Impacts on Infrastructure Increases in very hot days and heat waves Impact on lift-off load limits at high-altitude or hot-weather airports with insufficient runway lengths, resulting in flight cancellations or limits on payload (i.e., weight restrictions), or both Limits on periods of construction activity due to health and safety concerns Thermal expansion on bridge expansion joints and paved surfaces Concerns regarding pavement integrity (e.g., softening), traffic-related rutting, migration of liquid asphalt Rail-track deformities Increases in Arctic temperatures Longer ocean transport season and more ice-free ports in northern regions Possible availability of a northern sea route or a northwest passage Thawing of permafrost, causing subsidence of roads, rail beds, bridge supports (cave-in), pipelines, and runway foundations Shorter season for ice roads Rising sea levels, combined with storm surges More frequent interruptions to coastal and low-lying roadway travel and rail service due to storm surges More severe storm surges, requiring evacuation or changes in development patterns Inundation of roads, rail lines, and airport runways in coastal areas More frequent or severe flooding of underground tunnels and low-lying infrastructure
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Potential Impacts of Climate Change on U.S. Transportation Potential for closure or restrictions at several of the top 50 airports that lie in coastal zones, affecting service to the highest-density populations in the United States Erosion of road base and bridge supports Reduced clearance under bridges Changes in harbor and port facilities to accommodate higher tides and storm surges Increases in intense precipitation events Increases in weather-related delays and traffic disruptions Increased flooding of evacuation routes Increases in airline delays due to convective weather Increases in flooding of roadways, rail lines, subterranean tunnels, and runways Increases in road washout, damages to rail-bed support structures, and landslides and mudslides that damage roadways and tracks Increases in scouring of pipeline roadbeds and damage to pipelines More frequent strong hurricanes (Category 4–5) More frequent interruptions in air service More frequent and potentially more extensive emergency evacuations More debris on roads and rail lines, interrupting travel and shipping Greater probability of infrastructure failures Increased threat to stability of bridge decks Impacts on harbor infrastructure from wave damage and storm surges
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Potential Impacts of Climate Change on U.S. Transportation increasing the exposure of people and businesses to harm from extreme weather. The Atlantic and Gulf Coasts are particularly vulnerable because they have already experienced high levels of erosion, land subsidence, and loss of wetlands. Seven of the 10 largest U.S. ports (by tons of traffic), as well as significant oil and gas production facilities, are located on the Gulf Coast, an area whose vulnerability to disruption and damage was amply demonstrated during the 2005 tropical storm season. Sea level rise and coastal flooding also pose risks for the East Coast, as well as the Pacific Northwest and parts of the California Coast. The vulnerability of transportation infrastructure to climate change will extend beyond coastal areas. For example, watersheds supplying water to the St. Lawrence Seaway and the Great Lakes, as well as the Upper Midwest river system, are likely to experience drier conditions, resulting in lower water levels and reduced capacity to ship agricultural and other bulk commodities, although a longer shipping season could offset some of the adverse economic effects. Thawing permafrost in Alaska is already creating settlement and land subsidence problems for roads, rail lines, runways, and pipelines. Higher temperature extremes (mainly heat waves) in some U.S. regions could lead to more frequent buckling of pavements and misalignment of rail lines. More severe weather events with intense precipitation could increase the severity of extensive flooding events, such as the storms that plagued the Midwest during the 1993 flooding of the Mississippi and Missouri River system, the Chicago area in 1996, and the Houston region during Tropical Storm Allison in 2001. Flooding of a waterway system can knock out barge operations on the river itself, rail operations on rights-of-way adjacent to the river, and even highway approaches to bridges crossing flooded rivers. Not all climate change impacts will be negative. For example, the marine transportation sector could benefit from more open seas in the Arctic, creating new and shorter shipping routes and reducing transport time and costs. In cold regions, expected temperature rises, particularly decreases in very cold days and later onset of seasonal freezes and earlier onset of seasonal thaws, could mean reduced costs of snow and ice control for departments of transportation and safer travel conditions for passenger vehicles and freight. Recommendation 1: Federal, state, and local governments, in collaboration with owners and operators of infrastructure,
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Potential Impacts of Climate Change on U.S. Transportation such as ports and airports and private railroad and pipeline companies, should inventory critical transportation infrastructure in light of climate change projections to determine whether, when, and where projected climate changes in their regions might be consequential. These inventories would need to be updated periodically as new scientific knowledge about climate change becomes available. This would be a relatively low-cost activity because a large portion of the necessary information and tools [e.g., geographic information systems (GIS)] is likely to be available. The inventorying process itself should also help identify with greater precision the data needed from climate scientists on transportation-relevant climate changes. DECISION FRAMEWORK Transportation decision makers have an opportunity now to prepare for projected climate changes. Finding: Public authorities and officials at various governmental levels and executives of private companies are continually making short- and long-term investment decisions that have implications for how the transportation system will respond to climate change in the near and long terms. Recommendation 2: State and local governments and private infrastructure providers should incorporate climate change into their long-term capital improvement plans, facility designs, maintenance practices, operations, and emergency response plans. Taking measures now to evaluate and protect the most vulnerable infrastructure should pay off by diminishing near-term maintenance expenditures and reducing the risk of catastrophic failure, with its toll on human life and economic activity (see Box S-2, which presents a six-step approach for determining appropriate investment priorities). Such measures might include strengthening or elevating some coastal roads, rail lines, and bridges, particularly those that serve as evacuation routes, or upgrading parallel routes where they are available. In the longer term, relocation
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Potential Impacts of Climate Change on U.S. Transportation BOX S-2 Decision Framework for Transportation Professionals to Use in Addressing Impacts of Climate Change on U.S. Transportation Infrastructure Assess how climate changes are likely to affect various regions of the country and modes of transportation. Inventory transportation infrastructure essential to maintaining network performance in light of climate change projections to determine whether, when, and where the impacts could be consequential. Analyze adaptation options to assess the trade-offs between making the infrastructure more robust and the costs involved. Consider monitoring as an option. Determine investment priorities, taking into consideration the criticality of infrastructure components as well as opportunities for multiple benefits (e.g., congestion relief, removal of evacuation route bottlenecks). Develop and implement a program of adaptation strategies for the near and long terms. Periodically assess the effectiveness of adaptation strategies and repeat Steps 1 through 5. of rights-of-way farther inland or installation of costly storm barrier systems to protect selected areas (e.g., parts of New York City or Miami) might be considered. Prudent choices today could avoid some of these costs. Finding: The significant costs of redesigning and retrofitting transportation infrastructure to adapt to potential impacts of climate change suggest the need for more strategic, risk-based approaches to investment decisions. Traditionally, transportation decision makers have not taken full advantage of quantitative, risk-based approaches that incorporate uncertainty and probabilistic assessments in making investment and design decisions. Nor will past trends provide a reliable guide for future plans and designs as they relate to climate. Recommendation 3: Transportation planners and engineers should use more probabilistic investment analyses and design
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Potential Impacts of Climate Change on U.S. Transportation approaches that incorporate techniques for trading off the costs of making the infrastructure more robust against the economic costs of failure. At a more general level, these techniques could also be used to communicate these trade-offs to policy makers who make investment decisions and authorize funding. One model is the California Seismic Retrofit Program, which uses a risk-based approach for analyzing vulnerability to earthquakes and the criticality of highway bridges to determine priorities for retrofitting and replacement. Adapting such techniques to address climate change will require continuing education of current planners and engineers and training of future professionals. It will also require educating policy makers to gain their support and may well necessitate new eligibility criteria in funding programs and new funding sources so the investments identified by the application of these techniques can be made. DATA AND DECISION SUPPORT TOOLS Transportation decision makers note that one of the most difficult aspects of addressing climate change is obtaining the relevant information in the form needed for planning and design purposes. Specifically, as noted earlier, climate change is understood with greatest confidence as a global phenomenon, while transportation planners need local and regional climate projections. They also need a better understanding of how projected climate changes, such as changes in temperature and precipitation, will affect the environment (e.g., soil moisture, runoff) in which the infrastructure is situated, which will vary from region to region. Finding: Transportation professionals often lack sufficiently detailed information about expected climate changes and their timing to take appropriate action. Simply put, transportation professionals, climate scientists, hydrologists, and others have not communicated well. Recommendation 4: The National Oceanic and Atmospheric Administration, the U.S. Department of Transportation
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Potential Impacts of Climate Change on U.S. Transportation (USDOT), the U.S. Geological Survey, and other relevant agencies should work together to institute a process for better communication among transportation professionals, climate scientists, and other relevant scientific disciplines, and establish a clearinghouse for transportation-relevant climate change information. All professions should benefit from the collaboration. Transportation professionals would be encouraged to define with greater precision the climate data needed to make better transportation decisions, such as temperature and precipitation thresholds at finer-grained geographic scales or climate conditions that would create unacceptable performance outcomes. Climate scientists would be challenged to elaborate on the possibilities and limitations of projecting the impacts of climate change at the levels of geographic specificity that are most useful for transportation planners. And hydrologists and others would be challenged to consider how the environment would influence these effects and their impacts on transportation infrastructure. Finding: Better decision support tools are also needed to assist transportation decision makers. Recommendation 5: Ongoing and planned research at federal and state agencies and universities that provide climate data and decision support tools should include the needs of transportation decision makers. For example, the research program of the USDOT Center for Climate Change and Environmental Forecasting could be charged with expanding its existing research program in this area and provided the necessary funding. Needed tools include highly accurate digital elevation maps in coastal areas for forecasting the effects of flooding and storm surge heights; GIS that can be used to map the locations of critical infrastructure, overlaid with information on climate change effects (e.g., sea level rise, permafrost melt); greater use of scenarios that include climate change in the development of long-range regional transportation plans to pinpoint likely vulnerabilities and ways to address them; and better network models for examining the systemwide effects of the loss of critical transportation infrastructure links.
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Potential Impacts of Climate Change on U.S. Transportation ADAPTATION OPTIONS Numerous studies have examined ways of mitigating the transportation sector’s contribution to global warming from GHG emissions. Far less attention has been paid to the potential impacts of climate change on U.S. transportation and how transportation professionals can best adapt to climate changes that are already occurring and will continue to occur into the foreseeable future, even if drastic mitigation measures were taken today. Operational Responses Climate extremes and abrupt changes, such as storms and precipitation of increased intensity, will require near-term operational responses from transportation providers. U.S. transportation providers already address the impacts of weather on transportation system operations in a diverse range of climatic conditions. For example, snow and ice control accounts for about 40 percent of annual highway operating budgets in the northern states. Likewise, hurricane planning has become a major focus of transportation operations in the Gulf Coast states, where transportation providers are forging close relationships with emergency responders to handle severe weather events. As climate changes induce new extremes, operational responses are likely to become more routine and proactive than today’s approach of treating severe weather on an ad hoc, emergency basis. For example, if hurricanes increase in intensity, as is likely to be the case, establishment of evacuation routes and use of contraflow operations may become as commonplace as the current use of snow emergency routes in the Northeast and Midwest. More accurate and timely weather prediction and communication of storm warnings in real time to those potentially in harm’s way will become more important. Finding: Projected increases in extreme weather and climate underscore the importance of emergency response plans in vulnerable locations and require that transportation providers work more closely with weather forecasters and emergency planners and assume a greater role in evacuation planning and emergency response. Recommendation 6: Transportation agencies and service providers should build on the experience in those locations
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Potential Impacts of Climate Change on U.S. Transportation where transportation is well integrated into emergency response and evacuation plans. Monitoring and Use of Technology Monitoring infrastructure conditions, particularly the impacts of extreme climate changes, offers an alternative to preventive retrofitting or reconstruction of some facilities. In Alaska, for example, the Alyeska Pipeline Company constantly monitors the right-of-way of the Trans-Alaska Pipeline System to spot land subsidence problems, particularly along the 800 miles of pipeline elevated on vertical supports. Alaskan engineers also closely monitor bridge supports that are experiencing damage from earlier winter runoff and increased stream flow. In the future, sensors and other smart technologies could be embedded in the infrastructure to monitor climate conditions and impacts. Finding: Greater use of technology would enable infrastructure providers to monitor climate changes and receive advance warning of potential failures due to water levels and currents, wave action, winds, and temperatures exceeding what the infrastructure was designed to withstand. Recommendation 7: Federal and academic research programs should encourage the development and implementation of monitoring technologies that could provide advance warning of pending failures due to the effects of weather and climate extremes on major transportation facilities. Sharing of Best Practices As the climate changes, many U.S. locations will experience new climate-induced weather patterns. Finding: The geographic extent of the United States—from Alaska to Florida and from Maine to Hawaii—and its diversity of weather and climate conditions can provide a laboratory for identifying best practices and sharing information as the climate changes. Recommendation 8: The American Association of State Highway and Transportation Officials (AASHTO), the Federal
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Potential Impacts of Climate Change on U.S. Transportation Highway Administration, the Association of American Railroads, the American Public Transportation Association, the American Association of Port Authorities, the Airport Operators Council, associations for oil and gas pipelines, and other relevant transportation professional and research organizations should develop a mechanism to encourage sharing of best practices for addressing the potential impacts of climate change. This effort should build on existing technology transfer mechanisms, such as AASHTO’s technology-sharing program. Technology should be defined broadly to include probabilistic decision-making tools, as well as monitoring technologies, new materials, and operating and maintenance strategies. Design Changes Environmental factors are integral to the design of transportation infrastructure. Conditions such as temperature, freeze–thaw cycles, and duration and intensity of precipitation determine subsurface and foundation design, choice of materials, and drainage capacity. Engineers, however, have given little thought to whether current design standards are sufficient to accommodate climate change. For example, will drainage capacity be adequate for expected increases in intense precipitation events? Many infrastructure components are currently designed for the 100-year storm—an event of such severity that it occurs, on average, once in 100 years. But projections indicate that what is today’s 100-year precipitation event is likely to occur every 50 or perhaps even every 20 years by the end of the current century. What new materials might be needed when very hot temperatures and heat waves become more frequent? Are infrastructure components sufficiently strong to withstand the forces of larger and more frequent storm surges and more powerful wave action, the effects of which were vividly demonstrated when Hurricane Katrina simply lifted bridge decks off their supporting structures? Finding: Reevaluating, developing, and regularly updating design standards for transportation infrastructure to address the impacts of climate change will require a broad-based research and testing program and a substantial implementation effort.
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Potential Impacts of Climate Change on U.S. Transportation Developing consensus standards is a time-consuming process. Changes in design practices tend to be incremental, and building to higher standards must be weighed against the cost involved. Thus there is a need for a selective, risk-based approach to making changes in standards that focuses first on long-lived facilities, such as bridges and large culverts. A good model is the congressionally mandated National Earthquake Hazard Reduction Program, begun in 1977, which established a research effort and a coordination mechanism designed to reduce the risks to life and property from earthquakes through standards that would afford different levels of protection for different levels of risk. If a similar program is to be launched to address climate change in a timely manner, it should be initiated soon. Recommendation 9: USDOT should take a leadership role, along with those professional organizations in the forefront of civil engineering practice across all modes, to initiate immediately a federally funded, multiagency research program for ongoing reevaluation of existing and development of new design standards as progress is made in understanding future climate conditions and the options available for addressing them. A research plan and cost proposal should be developed for submission to Congress for authorization and funding of this program. The initial focus should be on essential links in transportation networks, particularly those vulnerable to climate change in coastal or other low-lying areas in riverside locations. Recommendation 10: In the short term, state and federally funded transportation infrastructure rehabilitation projects in highly vulnerable locations should be rebuilt to higher standards, and greater attention should be paid to the provision of redundant power and communications systems to ensure rapid restoration of transportation services in the event of failure. The development of appropriate design standards to accommodate climate change is only one of several possible adaptation strategies. Finding: Federal agencies have not focused generally on adaptation in addressing climate change.
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Potential Impacts of Climate Change on U.S. Transportation Recommendation 11: USDOT should take the lead in developing an interagency working group focused on adaptation. This initiative would not necessarily require new funding beyond that recommended above. Better collaboration among agencies could help focus attention on adaptation issues and shape existing research programs. Transportation Planning and Land Use Controls One of the most effective strategies for reducing the risks of climate change is to avoid placing people and infrastructure in vulnerable locations. Transportation planners currently consider expected land use patterns when forecasting future travel demand and infrastructure needs. However, they rarely question whether such development is desirable, much less what effects climate change might have on the provision and development of infrastructure in vulnerable locations. In part, this situation stems from governance arrangements. States, regional authorities, and the private sector are responsible for large-scale transportation investment decisions, but local governments and a few states control land use decisions through comprehensive plans, zoning ordinances, permitting, and building codes. Finding: Transportation planners are not currently required to consider climate change impacts and their effects on infrastructure investments, particularly in vulnerable locations. Recommendation 12: Federal planning regulations should require that climate change be included as a factor in the development of public-sector long-range transportation plans; eliminate any perception that such plans should be limited to 20 to 30 years; and require collaboration in plan development with agencies responsible for land use, environmental protection, and natural resource management to foster more integrated transportation–land use decision making. Current surface transportation legislation encourages such collaboration. During reauthorization, requiring transportation planners to both consider climate change and collaborate with land use planners in the preparation of public-sector long-range plans could go a long way toward putting these issues on the table. At the same time, any strategy employing land use controls to address climate change would need to build consen-
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Potential Impacts of Climate Change on U.S. Transportation sus among key decision makers in transportation and land use, probably at the regional level—a challenging proposition. Finding: Locally controlled land use planning, which is typical throughout the country, has too limited a perspective to account for the broadly shared risks of climate change. Insurance Private insurers may be able to accomplish what government cannot in terms of land use control. Some major insurers, for example, are refusing to write new or renew existing homeowners’ policies in areas already vulnerable to hurricanes and other severe storms, which could intensify in a warming climate. Florida, Texas, Louisiana, Mississippi, Hawaii, New York City, and Long Island are among the areas affected thus far. Some states have stepped up to become insurers of last resort for coastal homes and businesses, but the high costs of providing coverage are unlikely to be sustainable. Moreover, the provision of insurance in hazard-prone areas that is not actuarially based is bad public policy. The federal government is the insurer of last resort for homeowners in specially designated flood hazard areas. The National Flood Insurance Program of the Federal Emergency Management Agency (FEMA) provides homeowners with below-cost insurance. In return, the local community must adopt and enforce floodplain management measures, including building code ordinances for new construction and rebuilding after a disaster, to reduce flood damage. Critics contend that in practice, the program has resulted in more development than would otherwise have occurred in these areas. Moreover, the accuracy of flood insurance rate maps (FIRMs) used to determine program eligibility is woefully inadequate, despite a mapping modernization program. Flood hazard area boundaries are keyed to the 100-year storm, and base elevation data are inadequate. Finding: The National Flood Insurance Program and the FIRMs used to determine program eligibility do not take climate change into account. Recommendation 13: FEMA should reevaluate the risk reduction effectiveness of the National Flood Insurance Program and the FIRMs, particularly in view of projected increases in
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Potential Impacts of Climate Change on U.S. Transportation intense precipitation and storms. At a minimum, updated flood zone maps that account for sea level rise (incorporating land subsidence) should be a priority in coastal areas. New Organizational Arrangements The impacts of climate change do not follow modal, corporate, or jurisdictional boundaries, yet decision making in the transportation sector is structured around these boundaries. Transportation planning is conducted primarily at the regional level, often through a bottom-up process that starts with local jurisdictions. Railroads, trucking, and waterborne commerce are largely private enterprises with varying levels of federal participation. Thus, existing institutional arrangements are not well suited to addressing climate change. Some models of cross-jurisdictional cooperation exist, such as regional authorities for specific facilities (e.g., the Alameda Corridor) and multistate emergency response agreements. In addition, there are models of state-mandated regional authorities, as is the case for regional air quality improvement authorities. Organizational arrangements suited to addressing the impacts of climate change may require state or federal action. Finding: Current institutional arrangements for transportation planning and operations were not organized to address climate change and may not be adequate for the purpose. Recommendation 14: Incentives incorporated in federal and state legislation should be considered as a means of addressing and mitigating the impacts of climate change through regional and multistate efforts. For example, states could use updated FIRMs or their own state maps to identify geographic areas vulnerable to climate change and craft policies for restricting transportation investments and limiting insurance in these locations. CONCLUDING THOUGHTS The committee finds compelling scientific evidence that climate change is occurring and that it will trigger new, extreme weather events and could possibly lead to surprises, such as more rapid than expected rises in
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Potential Impacts of Climate Change on U.S. Transportation sea levels or temperature changes. Every mode of transportation will be affected as climate change poses new and often unfamiliar challenges to infrastructure providers. The committee urges that the transportation community start now to confront these challenges. A strong federal role is needed to implement many of the committee’s recommendations that require broad-based action or regulation, such as creation of a clearinghouse for information on transportation and climate change, the research program to reevaluate existing and develop new design standards for addressing climate change, creation of an interagency working group on adaptation, changes in federal regulations regarding long-range planning guidelines and infrastructure rehabilitation requirements, and reevaluation of the National Flood Insurance Program. Many of the committee’s recommendations, however, need not await federal action. Local governments and private infrastructure providers can begin to identify critical infrastructure that is particularly vulnerable to climate change. Professional organizations can begin to amass examples of best practice, and planners and climate scientists at local universities and research institutes can begin to collaborate on the development of regional scenarios of likely transportation-related climate changes and the data needed to analyze their impacts. The most important step, however, is for transportation professionals to acknowledge that the time has come to confront the challenges posed by climate change and to incorporate the most current scientific knowledge into the planning, design, construction, operation, and maintenance of transportation systems.