Chapter 9: Conclusion
Many DOTs and MPOs are beginning to incorporate climate change issues into their transportation planning processes. Within a few years, it is likely that virtually all new transportation plans will include explicit reference to the effects of transportation on climate change and the role of transportation in mitigating these effects. Many plans will also likely address the threats that climate change poses to the transportation system and potential adaptive responses.
While they do not explicitly require the inclusion of climate change considerations, the current federal transportation planning regulations include a number of requirements that generally align with climate change mitigation and adaptation. This occurs most directly in metropolitan transportation planning factor that requires that plans "protect and enhance the environment [and] promote energy conservation”.
The current practice for incorporating climate change into transportation planning varies widely by agency. Climate change can appear in the vision, goals, policies, strategies, trends and challenges, and performance measures of LRTPs. Some plans merely recognize that climate change is an issue that relates to transportation and begin to point out the relevance of existing plans and strategies to climate change. Other plans make climate change more central to their goals and policies.
Absent any federal action, the treatment of climate change in transportation planning is likely to continue to vary depending on the interests and concerns of local stakeholders, the size of agencies and their capacity to address climate change, and the vulnerabilities specific to regions and their transportation systems. A number of agencies DOTs and MPOs are waiting on decisions or recommendations from state agencies or committees on how they should address climate change. Others see a need for greater involvement from federal or state government in climate change issues. Many agencies are wary of taking steps to change their planning process before more direction from higher government levels is provided.
Small MPOs in particular may benefit from higher level guidance on how and where to incorporate climate change in LRTPs. Small MPOs have fewer resources and less power to set policy precedents than do larger MPOs. The potential burden imposed by future climate change regulations at the state or federal levels is likely greater for small MPOs.
The quantification of GHG emissions in the transportation planning process is a new challenge for transportation agencies. While the estimation of mobile source CO2 emissions is conceptually simpler than the estimation of criteria pollutant emissions that most transportation agencies already do, there are some unique challenges with the quantification of GHGs, including the following:
- There are often inconsistencies between the transportation components of a state-level GHG inventory and forecast (based on fuel sales data) and a metropolitan-level GHG inventory and forecast (based on VMT estimates from a travel demand model). As state-level climate change initiatives filter down to the MPO level, these inconsistencies will need to be reconciled.
- There are uncertainties regarding the appropriate geographic scale for estimation of project-level GHG emissions. Regional level analyses compare GHG emissions between broad packages of modal and land development strategies. Some agencies argue that quantitative analyses are not useful at finer grains, because GHG emissions are essentially determined at the regional level. Other agencies are proceeding with analyses down to the project level.
- The current EPA emissions models are not well-suited for analysis of the GHG impacts of transportation plans. The CO2 emission factors in MOBILE6 do not vary with vehicle speed or driving cycle, and thus are inappropriate for any kind of detailed analysis of transportation plan or project-level emissions, which are likely to involve changes to congestion levels and speeds. The MOVES2004 model does have GHG emission factors that vary with speed and driving cycle, but rather than using the MOVES2004 current interface, users must manually modify the MOVES database and create specific driving cycles in order to take advantage of this information. This presents a challenge to many users of the model, and also makes it cumbersome to analyze a large number of scenarios.
- Given the importance of a life-cycle approach to GHG emissions analysis, there is uncertainty regarding the need to estimate emissions resulting from transportation system construction and maintenance, as opposed to system use. Methods to estimate construction GHG emissions are poorly developed.
Many transportation agencies are anticipating the need to develop and quantify the benefits of strategies to reduce GHG emissions. A number of DOTs and MPOs have been involved in this exercise through their participation in state climate action plans. A few MPOs are taking steps to incorporate GHG mitigation into their planning, prompted by state mandates. There is concern among some transportation agencies that many of the most effective mitigation strategies are outside their sphere of direct influence (such as vehicle fuel efficiency, alternative fuels, and land use), while other potentially effective strategies (such as widespread use of roadway pricing) may be politically difficult.
Most transportation agencies are not currently seeking to incorporate climate change adaptation measures into long range planning. While there is general recognition of the threat that climate change poses to transportation infrastructure, agencies feel that significant impacts are at least several decades away, so there is little sense of urgency. In addition, the large uncertainty in the location and magnitude of impacts makes agencies reluctant to take major action on adaptation, given the multitude of other pressing demands for DOTs and their funding limitations. Over the next several years, as more sea level rise studies are completed and scientists improve the precision of climate change forecasts, adaptive responses are likely to be more substantially incorporated into long range planning.
