In 2008, the Federal Highway Administration (FHWA) assembled 13 federal agencies to form the Interagency Working Group on Transportation, Land Use, and Climate Change. The Working Group's goal was to identify opportunities to align federal programs and resources to support regional communities in achieving GHG emission reductions and preparing for potential climate change impacts through transportation and land use planning decisions. The Working Group identified two focus areas where federal agencies could begin to align efforts to address climate change:
In 2009, the Working Group selected Cape Cod, Massachusetts as a pilot area to facilitate and enhance integrated regional and intermodal gateway mobility planning at the state, regional, and local levels. The U.S. Department of Transportation (USDOT) Volpe National Transportation Systems Center (Volpe Center) began the resulting Interagency Transportation, Land Use, and Climate Change Pilot Project (Pilot Project) in early 2010 along with FHWA, the National Park Service (NPS), and the U.S. Fish and Wildlife Service (FWS). These agencies viewed the Pilot Project as an opportunity to address GHG reduction and transportation-based adaptation to climate change and to pilot and evaluate scenario planning as a method for doing so.
The Pilot Project intended to address the following goals:
The nation's transportation system contributes significantly to overall U.S. GHG emissions and, as a result, to climate change, which is causing effects, such as SLR, that will negatively impact the transportation system. Therefore, attempts within the transportation field to address climate change entail two components: mitigation and adaptation. Mitigation encompasses activities aimed at reducing GHG emissions from transportation infrastructure and activities, and adaptation refers to activities aimed at increasing the resiliency of the transportation network (or specific infrastructure assets) when confronted with expected, or actual, climate change impacts. Federal, state, regional, and local government agencies and partners who are involved in transportation, land use, emergency management, and related areas share the responsibility for mitigation and adaptation within the transportation context.
The Environmental Protection Agency (EPA) defines a GHG as any gas that traps heat in the atmosphere. Certain GHGs, like carbon dioxide, nitrous oxide, and methane, occur naturally in the atmosphere but are also produced through the combustion of fossil fuels and other industrial processes. These additional sources of GHG emissions trap extra heat in the atmosphere, causing shifts in the planet's climate. Transportation represents a significant source of GHG emissions, both in the U.S. and worldwide. The EPA estimates that U.S. tailpipe emissions represent 27 percent of the country's total GHG emissions and five percent of global GHG emissions. Reducing transportation's contribution to overall GHG emissions and the resulting changes in climate will require mitigation strategies that reduce fossil fuel consumption and the carbon content of fuels. These include, but are not limited to, improving system and operational efficiencies, reducing growth of VMT, transitioning to lower GHG fuels, and improving vehicle technologies. A more thorough discussion of GHG emission reduction strategies for Cape Cod is presented in Section III, and a list of strategies is in Appendix F: Potential GHG Reduction Strategies.
While lowering transportation GHG emissions is an important strategy for reducing the long-term effects of climate change, mitigation will likely do little in the short-term to alter climate change processes already underway. Adaptation to the anticipated effects of climate change is a climate change strategy equally important as mitigation. Adaptation consists of five primary actions: repair and maintenance, reconstruction/strengthening, relocation, abandonment, and redundancy.
Climate change stands to have effects on transportation infrastructure in a variety of ways. The expected effects differ by region of the U.S. based on geographical, meteorological, and other features, but common effects include rising sea levels, increasingly frequent and intense storms, higher average temperatures, greater levels of precipitation, and drought., An increasingly volatile and severe climate will necessitate transportation infrastructure that is more resilient, but the uncertainty of climate change will also demand planning practices that anticipate the range of potential changes that may occur over the lifespan of new and existing infrastructure. In certain cases, fortifying infrastructure to withstand wider temperature extremes and more severe storm activity will suffice but adaptation to climate change, particularly in low-lying coastal areas, may require difficult decisions about relocating or abandoning at-risk facilities.
Scenario planning is a technique that allows organizations to prepare for potential future conditions. Instead of planning for a single predicted future and risking significant loss should reality diverge from prediction, military strategists, and later corporate strategic planners, began developing ranges of possibilities for the future that allowed them to identify common strategies to pursue in preparation for all of the possibilities. This risk-mitigation scenario planning has been used to address climate change adaptation, as it accommodates preparing for multiple possible levels of impact, but it has not yet been applied widely by the transportation community for climate change adaptation or mitigation. The diagram in Figure 1 illustrates this approach.
NPS has applied this type of scenario planning to climate change adaptation, with some implications for transportation infrastructure and access. The NPS approach allows park managers to develop possible future climate change scenarios, in terms of SLR, precipitation, and other effects, that could affect parks, and evaluate responses to each that protect natural, cultural, and physical resources, including buildings, roads, bridges, and other facilities. Given the uncertainty of climate change, this approach allows park managers to assess which responses are most likely to be beneficial across all scenarios or at least those scenarios determined to be most likely. 
Figure 1: Risk-mitigation scenario planning allows organizations to develop strategies that will prepare them for a range of possible futures.
According to FHWA, scenario planning is being used by MPOs nation-wide is "an analytical tool that can help transportation professionals prepare for what lies ahead. Scenario planning provides a framework for developing a shared vision for the future by analyzing various forces that affect growth." The use of scenario planning by MPOs for evaluating transportation and land use issues and decisions follows an approach similar to that of alternatives analysis, wherein several alternatives are developed and evaluated, and one outcome is selected. However, in using scenario planning, MPOs are able to consider the interactions between many factors, and use extensive public engagement to develop and assess the future scenarios. Thus, instead of establishing a range of possible future conditions and shaping decisions to address as many of those conditions as possible, this land use and transportation-focused application of scenario planning allows stakeholders to evaluate the consequences of several courses of action and select the outcome and course of action that best meets the goals of the community. The diagram in Figure 1 illustrates this approach.
Figure 2: The use of scenario planning by MPOs enables organizations to select a shared vision for the future from a range of possibilities and to develop corresponding strategies designed to work towards that future. Source: NPS Climate Change Response Program.
The FHWA Scenario Planning Guidebook documents the application of scenario planning to transportation and land use planning. However, FHWA acknowledges that "next generation" scenario planning for transportation can also take into account a range of factors that have not traditionally been considered in the transportation system, including climate change.
As a next generation scenario planning effort, the Pilot Project was issue-focused on climate change and multiple agency involvement. Rather than developing broad transportation and land use goals or determining strategies for goals that had already been established through a planning process, the Pilot Project took as a starting point the goals of reducing GHG emissions and preparing for climate change impacts through agencies' and other stakeholders' transportation and land use decisions. In addition, the Pilot Project determined specific growth projections in population and employment for 2030 that were used as targets during the scenario planning process. The Pilot Project intended to use scenario planning as an educational tool to engage and inform a broad group of stakeholders around climate change issues through an integrated planning approach.
This project did not result in the development of a regional transportation plan (RTP), nor did it lead to decisions about development patterns at the neighborhood or parcel level, or prescribe zoning or development types. Instead, participants worked at a regional scale to indicate the desired locations for preservation, development, and improvements to transportation services based on GHG emissions and climate-change impact considerations. The impact of these regional determinations was then evaluated by important indicators, or measures of performance, which were selected based on the goals of the exercise, the data available, and the scenario planning tool being employed.
This process allowed for the testing of the relationships among transportation, development, GHG emissions, and climate change impacts, and raised awareness about the implications of transportation and land use decisions on climate change issues. The outcomes of the scenario planning process are anticipated to help inform future versions of the RTP as well as other state, local, and federal agency transportation and development plans for the region.