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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2010. Assessing Mechanisms for Integrating Transportation-Related Greenhouse Gas Reduction Objectives into Transportation Decision Making. Washington, DC: The National Academies Press. doi: 10.17226/22967.
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Web-Only Document 152: Assessing Mechanisms for Integrating Transportation-Related Greenhouse Gas Reduction Objectives into Transportation Decision Making National Cooperative Highway Research Program Michael Grant, Janet D’Ignazio, Jeff Ang-Olson, Anna Chavis, Frank Gallivan, Melinda Harris, Kathleen Rooney, Theresa Silla, Elizabeth Wallis, Sarah Siwek ICF International Fairfax, VA Contractor’s Final Report for NCHRP Project 20-24(64) Submitted January 2010 NCHRP

ACKNOWLEDGMENT This study was requested by the American Association of State Highway and Transportation Officials (AASHTO), and conducted as part of National Cooperative Highway Research Program (NCHRP) Project 20-24. The NCHRP is supported by annual voluntary contributions from the state Departments of Transportation (DOTs). Project 20-24 is intended to fund studies of interest to the leadership of AASHTO and its member DOTs. The research effort was managed by Michael Grant and Janet D’Ignazio of ICF International. Report authors included Jeff Ang-Olson, Anna Chavis, Janet D’Ignazio, Frank Gallivan, Michael Grant, Melinda Harris, Kathleen Rooney, Theresa Silla, and Elizabeth Wallis of ICF International. Sarah Siwek also provided substantial contributions. The work was guided by a technical working group chaired by Brian J. Smith which included Stuart P. Anderson, P.E.; Brad Beckham; Jane D. Hayse; Ronald F. Kirby; Chris Klaus; Therese W. McMillan; James Ritzman, P.E.; John H. Thomas, P.E.; Dr. John V. Thomas; Cecilia Ho; Janet Oakley; Robert Padgette; Rich Denbow; and DeLania Hardy. The project was managed by Andrew C. Lemer, Ph. D., NCHRP Senior Program Officer. COPYRIGHT PERMISSION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA, FMCSA, FTA, Transit Development Corporation, or AOC endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. DISCLAIMER The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research. They are not necessarily those of the Transportation Research Board, the National Research Council, or the program sponsors. The information contained in this document was taken directly from the submission of the authors. This report has not been edited by TRB.

NCHRP Project 20-24(64) Final Report iv TABLE OF CONTENTS Summary ..................................................................................................................................... vi 1. Introduction .......................................................................................................................... 1 1.1 Background ........................................................................................................................................... 1 1.2 Purpose and Scope of the Study ............................................................................................................ 5 1.3 Study Process ........................................................................................................................................ 7 1.4 Report Organization .............................................................................................................................. 8 2. Overarching Options for Establishing Transportation Requirements that Involve Targets .................................................................................................................................. 9 2.1 Geographic Level of Responsibility – State, MPO, or Local ............................................................... 9 2.2 Target Metric – Vehicle Miles Traveled or Greenhouse Gas Emissions ............................................ 14 2.3 Emissions Sources Covered – Light Duty Vehicles, All On-Road Vehicles, or All Transportation Sources ........................................................................................................................................................ 18 2.4 Measurement Benchmarks – Basis for Target Comparison ................................................................ 20 2.5 Regulatory Nature of Target – Mandatory or Voluntary .................................................................... 22 3. Assessments of Alternative Policy Mechanisms for Reducing Transportation GHGs .................................................................................................................................. 24 3.1 Policy Mechanisms Considered .......................................................................................................... 24 3.2 Criteria for Assessing Mechanisms .................................................................................................... 29 3.3 Assessment of Mechanisms ................................................................................................................ 29 3.4 Regulatory Transitions ........................................................................................................................ 44 4. Implications of Alternative Targets on Sample States and MPOs ................................ 46 4.1 Wide Diversity in State and MPO Characteristics .............................................................................. 47 4.2 Reduction in GHGs from Base Year .................................................................................................. 52 4.3 Reduction in GHGs per capita from Base Year .................................................................................. 54 4.4 Reduction in Relation to Projected Emissions .................................................................................... 55 4.5 Reduction in VMT .............................................................................................................................. 57 5. Analysis Tools and Techniques to Support Implementation of Policy Mechanisms ....................................................................................................................... 59 5.1 Measuring and Estimating VMT ........................................................................................................ 60 5.2 Forecasting VMT ................................................................................................................................ 62 5.3 Estimating and Forecasting GHG Emissions ...................................................................................... 67 5.4 Agency Forecasting Capabilities and Limitations .............................................................................. 69 5.5 Off-Model Tools and Techniques for GHG Reduction Strategy Analysis ......................................... 71 5.6 Summary of Findings on Analysis Tools and Techniques ................................................................. 74

NCHRP Project 20-24(64) Final Report v Appendix A: List of Workshop Participants ........................................................................... 75 Appendix B: Information on Market-Based Mechanisms ..................................................... 77 B.1 GHG Emissions Trading ...................................................................................................................... 77 B.2 Carbon Taxes ........................................................................................................................................ 84 Appendix C: Summary of Methodology for Analysis of Sample States and MPOs ............ 86

NCHRP Project 20-24(64) Final Report vi SUMMARY This report is the product of research supported by the National Cooperative Highway Research Program. (NCHRP) The objective of NCHRP Project 20-24(64) was to provide a factual basis for judging the merits of alternative methods that state departments of transportation (DOTs) and metropolitan planning organizations (MPOs) can use for managing GHG emissions from transportation. The project was undertaken to help policy makers to understand (a) how these alternative approaches to GHG emissions would affect states and metropolitan areas, (b) what approaches may be most effective for evaluating mobile-source GHG emission-management strategies, and (c) what particular tools are available to support implementation of these alternative approaches. Policy efforts are advancing to integrate climate change considerations into transportation decision making. New requirements for transportation agencies to integrate greenhouse gas (GHG) considerations into transportation decision making are currently being proposed and debated at both the national and state levels. Bills before the U.S. Senate and House of Representatives would require DOTs and MPOs to demonstrate effort to reduce GHG emissions as part of the statewide and metropolitan transportation planning process. Similar requirements have been proposed for the reauthorization of federal surface transportation legislation. Several states, including California, Washington, and New York, have already adopted requirements to address GHGs in transportation planning. These requirements are being considered in the context of a range of potential national climate change policy statements. Exhibit ES-1: Examples of Proposed and Existing Requirements for Integrating GHG Objectives into Transportation American Clean Energy and Security Act of 2009 (HR 2454, House-passed) Amends existing transportation planning processes to require states and MPOs in transportation management areas (TMAs) to develop targets and strategies for GHG emissions reductions. State and MPO plans must “contribute” to the achievement of the national emissions reductions targets. Clean Energy Jobs & American Power Act (Boxer/Kerry proposal) Amends existing transportation planning processes to require states and MPOs in TMAs to develop targets and strategies for GHG emissions reductions. MPOs must demonstrate progress in stabilizing and reducing GHG emissions to achieve state targets. Surface Transportation Authorization Act Of 2009 (Oberstar proposal) Requires states and MPOs in TMAs to set targets for GHG emissions reductions from surface transportation and incorporate strategies to meet targets into their plans. U.S. DOT, through performance measures, will verify that states and MPOs achieve progress towards national GHG goals. California’s SB 375 (Signed 2008) Requires the state to set GHG reduction targets for California’s 18 MPOs. MPOs must prepare long range plans that demonstrate how they will achieve the targets. Washington’s HB 2815 (Signed 2008) Requires the state to reduce light-duty vehicle miles traveled (VMT) per-capita 18% by 2020, 30% by 2035, and 50% by 2050. New York’s State Energy Plan (Adopted 2002) Calls for analyzing the energy and GHG emissions impacts of long range transportation plans and transportation improvement programs (TIPs). If enacted, any of the new federal requirements would have major implications for state DOTs and large MPOs. New requirements would likely necessitate enhancement to existing transportation analysis tools. The way the requirements are set could have equity implications, making it easier for some areas to

NCHRP Project 20-24(64) Final Report vii comply than others. The nature of the requirements could also steer investment in GHG reduction measures toward some types of projects and programs over others. Transportation agency executives need to understand the implications of these policy options. To provide that information, this study performed a comparative assessment of alternative policy mechanisms that would place requirements on transportation agencies to achieve GHG reductions in transportation planning and programming. Greenhouse gases are different from other air pollutants in important ways. Although the transportation community has had more than 15 years of experience addressing air quality issues within the transportation planning process, GHG emissions in several ways are different from the criteria air pollutants currently regulated under the Clean Air Act:  The environmental impact of most GHG emissions is the same regardless of where or when they are released.  GHGs encompass at least six different gases that generally have the same effect on climate, though some are more potent than others.  There are no means of using air quality monitoring data to designate nonattainment areas that exceed safe levels.  GHGs persist in the atmosphere for decades; thus cumulative emissions are important. Due to the global nature of GHGs, there is not a clear health basis for setting limits of GHG emissions for specific regions or states. Consequently, climate change concerns will likely require new types of policy mechanisms to achieve environmental objectives. Establishing GHG targets in transportation planning and programming involves decisions on several policy issues. The assessment described in this report highlights five key dimensions of GHG management policy. (Exhibit ES-2) Exhibit ES-2: Key Dimensions of Policies Associated with Integrating GHG Objectives into Transportation Planning and Programming Geographic Level of Implementation Target Metric Sources Covered Reduction Target based on Regulatory Nature of Target  States  MPOs  Subset of the largest MPOs  Other (county, municipality, multi-state region)  GHG emissions  Vehicle miles of travel (VMT)  Light-duty vehicles  All on-road vehicles  All transportation sources What units?  Total GHGs or VMT  GHGs or VMT per capita What baseline?  Base year (e.g., 1990)  Business-as-usual scenario forecast  Mandatory (with penalties)  Voluntary (with incentives/ disincentives) 1. What is the Appropriate Geographic Level of Implementation? There is no clearly effective approach to establishing boundaries for transportation GHG requirements. Unlike other air pollutants, where the geography of the air quality problem informs regulatory boundaries,

NCHRP Project 20-24(64) Final Report viii GHG emissions have a global effect. The geographic level of implementation has implications for the amount of GHGs covered under the requirement, the available strategies for reducing emissions, and the modeling requirements and staffing demands placed on transportation agencies.1  State-level requirements would cover all areas and avoid placing an unfair burden on urban areas. An advantage of a state-level requirement is that it would cover the entire geography of the U.S. An MPO-level requirement would cover a large portion of vehicle travel and transportation GHG emissions, but not the entire country. Approximately 70 percent of U.S. vehicle travel occurs in urbanized areas, and MPOs typically encompass these urbanized areas plus non- urbanized areas within the same county boundaries.  MPO-level requirements fit well with metropolitan transportation planning practices, but the large number and wide diversity of MPOs creates complexities. An advantage of an MPO-level requirement is that metropolitan transportation plans are fiscally constrained plans that identify capital investments and other strategies and must be updated on a regular cycle. Therefore, these plans are better suited toward conducting a regional emissions analysis than statewide long range plans, which often are policy-oriented, do not identify specific investments, and are not required by federal law to be updated on a regular cycle. Because of the large number of MPOs (385 currently), a disadvantage of a requirement that applies to all MPOs is the complexity of establishing and tracking attainment of targets, if under the purview of a federal entity, compared to state-level requirements. An advantage of a requirement that applies to larger MPOs is that fewer entities are regulated, while accounting for a relatively large share of transportation GHG emissions.  Current analytic tools are inadequate for VMT and GHG analysis at the statewide level and for small MPOs. Technical analysis capability is an important issue in determining the appropriate geographic level of implementation. Most state DOTs do not have statewide travel forecasting models capable of estimating vehicle travel or GHGs and evaluating reduction strategies. While a state-level requirement may benefit from the fact that state-level GHG inventories have been created for more than 30 states, these existing inventories are not highly detailed. A state-level requirement would place substantial resource demands on most DOTs to develop the necessary analytical tools; it also likely would require changes in the statewide transportation planning process. Upgrading analytical tools and changing the planning process could take several years. While an MPO-level requirement would also place resource demands on MPOs for modeling enhancements, many MPOs – particularly those in larger metropolitan areas – already have the basic building blocks for regional VMT and GHG analysis. The majority of MPOs, however, are small (with populations under 200,000) and have few staff and limited resources to handle new analytical requirements related to GHGs. In fact, the mean number of full time staff at MPOs with under 200,000 population is 3.2.2 2. Should a Requirement Focus on VMT or GHGs? Reducing VMT is one strategy to reduce transportation GHGs. Focusing on VMT could simplify measurement of progress and monitoring of compliance with targets. Yet transportation GHGs emissions are affected by factors other than VMT – vehicle fuel economy, fuel carbon content, and the efficiency of the system operations – and the utility of VMT as a proxy for GHGs diminishes as vehicles and fuels become more efficient. The selection of a VMT or GHG metric has implications for the types of 1 This study focused primarily on options of statewide or MPO-level implementation, and considered the option of requirements that would apply only to MPOs within Transportation Management Areas (TMAs). It did not evaluate other potential options such as a multi-state region. 2 General Accounting Office (GAO) 09-868 Metropolitan Planning Organizations, Options Exist to Enhance Transportation Planning and Capacity. September 2009.

NCHRP Project 20-24(64) Final Report ix compliance strategies that would be emphasized and the effectiveness of the requirement at achieving desired climate change benefits.  A GHG metric focuses directly on the outcome of interest. An advantage of using GHGs as a metric is that it is directly focused on the environmental outcome of interest – global climate change. In contrast, VMT is only one factor contributing to GHGs, and the link between VMT reduction and GHG reduction becomes weaker as fuel economy improves and low carbon fuels gain market share. For instance, the U.S. Department of Energy forecasts that between 2007 and 2035, light-duty VMT will grow by 53 percent while CO2 emissions from light-duty vehicles will decline by nearly 5 percent.3 A GHG metric accounts for all factors that affect GHG emissions from on-road vehicles – VMT, idling, vehicle fleets, and fuels. A GHG metric would encourage consideration of a wider range of reduction strategies to be implemented within the transportation planning process, and would allow better comparisons between different emissions sectors for an overall national climate strategy.  A VMT metric is more commonly used by transportation planners, but ignores the potential benefits associated with transportation system operations strategies and technologies. An advantage of a VMT requirement is that VMT is more straightforward for transportation agencies to analyze, since it does not account for vehicle fleet characteristics and fuel carbon content. Since transportation planning agencies only have limited influence on vehicle technologies and fuels, a focus on VMT relates directly to a primary driver of GHG emissions that transportation planning decision can influence. It also avoids the potential that an unexpected improvement or slower than expected improvement in vehicle and fuel characteristics would significantly impact the ability to meet a GHG target. A VMT metric, however, will not capture the potential GHG benefits of transportation system management and operations strategies, such as lower speed limits, traffic signal improvements and incident management programs that reduce traffic delay, or technology strategies, such as truck stop electrification.  A VMT-based requirement would place more emphasis on strategies that reduce vehicle travel demand, such as land use strategies, transit investments, bicycle and pedestrian investments, and ridesharing programs. A GHG-based requirement would enable reductions to be demonstrated through investments in improved system operations, and strategies that encourage the use of more efficient vehicle technologies and alternative fuels, as well as vehicle travel reduction. A GHG requirement can also account for reductions in non-road emissions. 3. What Emissions Sources Should Be Covered? A GHG-related transportation planning requirement could focus only on travel by light-duty vehicles (automobiles and light trucks), all motor vehicles, or all transportation sources (including railroads, air travel, and marine vessels).  Light-duty vehicles make up a majority of transportation GHG emissions and can be influenced directly by transportation planning decisions. Heavy truck travel is more difficult for DOTs and MPOs to influence, since it is closely tied to economic factors and much of it involves trips that extend beyond state or metropolitan area boundaries. In addition, transportation agencies have little influence over freight rail and commercial marine activity. Options available to DOTs and MPOs to reduce emissions from freight travel are largely restricted to reducing idling of vehicles, enabling more efficient movement of freight through specific corridors, and reducing emissions associated with specific port and intermodal facilities. 3 U.S. Department of Energy, Energy Information Administration, Annual Energy Outlook 2010 Early Release, December 2009. Summary Reference Case Tables A7 and A19. Available at: http://www.eia.doe.gov/oiaf/aeo/index.html.

NCHRP Project 20-24(64) Final Report x  Heavy-duty freight vehicles make up a disproportionately large share of GHG emissions compared to VMT. An advantage of including heavy trucks in a planning requirement is that they account for a disproportionate share of GHG emissions. While freight trucks make up only 7.5 percent of VMT nationally, they produce 35 percent of on-road transportation CO2 emissions.4 Excluding this source would fail to account for an important component of transportation GHG emissions, and for strategies that improve heavy truck efficiency. However, freight could potentially be addressed through policies at a national level, in which case freight may not need to be included in state or metropolitan analyses.  Non-road sources are not typically incorporated into the metropolitan or statewide transportation planning process. Including these sources would present challenges because non-road transportation is not part of most metropolitan transportation plans and programs. While state DOTs often help to plan and coordinate rail, marine, and air transportation, and some DOTs operate services, most DOTs do not invest in these systems. 4. How Might a Reduction Target be Set? The way that the target is set would make it easier for some states or MPOs to comply and more difficult for others, depending on factors such as growth rates and the opportunities to implement reduction strategies. A target could be set as a total reduction in transportation GHG emissions or VMT, or as a per- capita reduction. The target could be set in relation to a historic baseline year (e.g., a 20 percent reduction from 1990 levels), a current year, or a projected future baseline (e.g., a build-no build comparison). Another option is not to set a specific target but to simply require VMT or GHG analysis, which in turn might lead to a greater recognition of and consideration of climate change implications in decision making.  An advantage of setting a fixed target (e.g., total VMT or GHGs) is that it provides more certainty and provides a common metric to compare the impact of transportation reduction strategies against those focused on other sectors. However, uniform application of a VMT or GHG reduction target (e.g., a 20 percent reduction from 1990 levels is applied to all areas) may raise equity issues. It would be more challenging to meet this type of target in fast growing areas than slow growing ones.  An advantage of setting a per-capita target is that it would not penalize fast growing areas, and would provide more flexibility to DOTs and MPOs if their actual population growth differs substantially from projections. However, the total GHG reductions achieved through this type of target are less certain, since robust growth could overwhelm actual emission reductions even if the targets are met. In addition, a uniform per-capita target could raise different equity issues, since some areas (e.g., rural areas or slow growing areas) have fewer opportunities to reduce transportation GHGs.  Flexibility to establish different targets for different areas is an important consideration in the design of requirements, given the wide diversity in population, economic growth, travel options, and freight movement across states and metropolitan areas. An advantage of setting a target based on a historic year (e.g., in relation to 1990 levels) is that it would provide credit to states or regions that have taken early action to reduce GHG emissions. However, areas with high population growth would be more challenged to meet such an absolute target than areas with slower growth if uniform targets are established nationwide. The particular baseline year would determine how much targets account for historical trends. An advantage of setting a target in 4 On-road sources include passenger cars, light-duty trucks, medium-and-heavy duty trucks, motorcycles, and buses. Sources: Federal Highway Administration, Highway Statistics 2007, Table VM-1; U.S. Environmental Protection Agency, Inventory Of U.S. Greenhouse Gas Emissions and Sinks: 1990-2007, Table 2-15, April 15, 2009.

NCHRP Project 20-24(64) Final Report xi relation to a projected future baseline (e.g., in relation to forecast 2030 levels) is that it would help to level the playing field among states and MPOs, given their wide diversity in population and economic growth, as well as differences in opportunities to reduce motor vehicle emissions. This type of approach could be similar to a “build-no build” analysis that explores the impacts of a set of transportation investments in comparison to a scenario without these investments. Basing targets on forecasts, however, introduces some concerns about the legitimacy and reliability of forecasts used. Under any approach, consideration needs to be given to the appropriate role and targets for transportation planning agencies in the context of all sectors of the economy. 5. Should a Requirement be Mandatory or Voluntary? Emission reduction targets can be established to be mandatory or voluntary. A policy mechanism could mandate a certain level of reductions, with penalties for non-compliance (e.g., a VMT or emissions budget, similar to the emissions budgets established under the Clean Air Act requirement for transportation conformity) or it could encourage voluntary measures to achieve reductions, with incentives to motivate compliance (e.g., a VMT or emissions performance standard).  A mandatory budget would likely require more substantial modeling analysis. A mandatory budget would likely focus increased attention on strategies to achieve the target, just as the threat of not meeting conformity has been an impetus for some transportation agencies to invest in transportation demand management programs and other emissions reduction measures. It would necessitate greater care in setting realistic and achievable reductions, since failure to meet them would result in highway funding restrictions. As a result, a potential concern with a mandatory budget is that the target would be less ambitious than what some agencies could actually achieve. Given the pass-fail nature of a mandatory budget, it would likely require more effort to analyze the impacts of transportation strategies that have small impacts when close to meeting the target. Moreover, a fixed GHG budget would likely need to be revised on a rigorous schedule to accommodate changes in underlying assumptions regarding vehicle fuel efficiency or fuel carbon content. Performance standards may also need to be updated regularly, but there is less pressure to do so.  A performance standard would provide more flexibility to transportation agencies and might yield the same or more substantial GHG reductions as a mandatory budget. A voluntary performance standard would provide more flexibility to transportation agencies. In some cases, such as if significant incentives were provided, performance standards might encourage agencies to reduce transportation emissions beyond what would be required of them under a budget. However, the total GHG benefits of a target involving performance standards would be less certain than under a budget.  A requirement could combine elements of both budgets and performance standards. For example, a budget could establish minimum levels of reductions required of all DOTs or MPOs, and voluntary performance standards coupled with financial incentives could encourage additional reductions. Other transportation GHG policy approaches could be considered instead of or in addition to setting targets. In addition to establishing GHG-related targets for transportation plans, a number of other climate change-related policy mechanisms could be implemented that would directly affect transportation decision making. These mechanisms might be applied as a stand-alone requirement or could be included as a part of a target-based requirement.

NCHRP Project 20-24(64) Final Report xii  States and/or MPOs could be required to develop climate action plans. A climate action plan would identify GHG reduction strategies for all transportation sources, and potentially for all sectors of the economy. A multisector climate action plan could help to put transportation sources into context and enable better consideration and tradeoffs among sectors and modes of transportation, but some transportation strategies that emerge may be difficult to implement if they are not tied to transportation plans, programs, or funding, or if they are outside the control of transportation agencies.  Interagency consultation requirements could be adopted to cover all federal, state, and local stakeholder agencies involved in efforts to reduce GHG emissions. Consultation processes could be similar to those incorporated in the transportation air quality conformity process or other consultation processes that occur in transportation planning. Consultation could include other agencies that may not be as involved in these processes, such as economic development and land use agencies.  A requirement for implementing transportation emissions reduction strategies or prioritizing funding toward these strategies could replace or complement GHG target-based requirements. This approach could require implementation of specific types of transportation emissions reduction strategies or best management practices (BMPs). It could allow State DOTs or MPOs to select from a predetermined list of BMPs and receive credits or points for implementing specific measures in order to achieve a required number of points. This approach would be simpler to implement and less technically challenging than an approach requiring GHG or VMT forecasting, but it raises questions about the effectiveness of emissions reduction strategies in different contexts and applications and about the degree to which overall GHGs would be reduced. Alternatively, it could involve a requirement to prioritize funding for emissions reduction strategies before certain types of transportation investments (e.g., highway capacity improvements) could move forward, even if a target approach is implemented.  GHG analysis could be required at the transportation project level in connection with the National Environmental Policy Act (NEPA) process. This could focus increased attention on the contribution of individual investment decisions on GHG emissions. It would also raise challenging analytical issues, since isolating the GHG impacts of an individual project is difficult, and the impacts are generally small. Other climate change policies could indirectly affect transportation planning decisions through effects on travel demand, transportation funding, or revenues. Market-based mechanisms, such as carbon emissions trading and carbon taxes, are policy mechanisms that are being proposed at the national level and may be implemented along with transportation specific requirements. These mechanisms would indirectly affect transportation and could be implemented in conjunction with any of the policy mechanisms that are focused directly on transportation decision making. Policy makers should be aware of the potential indirect effects of these proposals on travel demand, funding, and revenues, and consider potential synergies of transportation requirements with these policies. Other policy considerations will influence the effectiveness of any new GHG requirements. The research described in this report was intended to assess advantages and disadvantages associated with different approaches to integrating GHG objectives into transportation decision making. The research demonstrates all approaches under consideration have both disadvantages and advantages; there is no one

NCHRP Project 20-24(64) Final Report xiii clearly optimal approach. In addition to their likely effectiveness in achieving GHG objectives, several other considerations will likely influence choices among the several approaches considered in this work:  Agencies’ technical and staff capacity to fulfill requirements – Any new requirements to analyze the GHG or VMT impacts of transportation plans and programs at the state or metropolitan level will likely require some improvements in transportation and land use modeling, either to account for better forecasts of VMT, congestion, and trips, or to better model the effects of land use and other strategies. Recognizing the large differences in forecasting capabilities among state DOTs and MPOs of different sizes suggests the need for some transition time and/or funding to ensure a minimum level of capability in forecasting, or an approach that does not require detailed modeling capabilities. This includes the consideration that it will take some time to build the necessary specialized technical skills within the numerous organizations for which these will be required. Transportation agencies have an interest in requirements that help to achieve GHG reductions while minimizing the burdens of having to conduct very time- consuming or complex analyses that only address very small or insignificant levels of emissions.  Planning as a means for influencing GHG reductions – While transportation planning can play an important role in contributing to GHG reductions, transportation agencies have limited control over many of the factors that influence GHGs, including changes in vehicles and fuels. The role of transportation agencies, therefore, needs to be considered in the context of the various factors that affect GHGs.  Integration into existing processes – Any new requirements should work in harmony with the existing transportation planning and project development requirements. New requirements might offer opportunities to better integrate transportation, land use (including housing and economic development considerations), and environmental planning, and should consider how they fit in with other climate change policies.  Equity considerations and unintended consequences – Under an approach that involves targets, a key challenge is setting appropriate targets that are fair and do not unduly burden particular areas at the expense of others. A “one size fits all” type of target applied to all states or MPOs would likely be unworkable and create difficult equity issues, given the wide differences in population growth rates, travel and land use patterns, and the ability to implement effective transportation strategies. If targets are only set for a subset of areas, such as large MPOs this might create an unintended consequence of pushing growth outside of metropolitan areas with the greatest potential to reduce emissions per capita. At whatever level GHGs are regulated, transportation agencies would like to play a key role in establishing targets to ensure they are achievable and meaningful yet do not compromise the ability to meet transportation needs.  Flexibility to meet changing conditions – Efforts to achieve GHG reductions should be flexible to respond to changing conditions, such as variations in population or economic growth and evolution in vehicle fleets. If specific targets are to be set (particularly under a mandatory budget), flexibility to adjust targets over time as necessary. Transportation system planning and management policies designed to influence emissions and levels of GHG may have significant impact on DOTs and MPOs. If such policies are to be feasible and effective, their designers should consider carefully the policies’ likely effectiveness and costs, the administrative burdens that compliance will place on agencies, and the equity of how costs and other burdens are distributed. As policy makers work to craft global climate change and transportation policies that may affect state DOTs and MPOs, it is essential to consider the strengths and weaknesses of various approaches so that the selected approach works to achieve meaningful reductions in GHG emissions while minimizing compliance burdens, ensuring fairness, and supporting cost-effective strategies.

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TRB’s National Cooperative Highway Research Program (NCHRP) Web-Only Document 152: Assessing Mechanisms for Integrating Transportation-Related Greenhouse Gas Reduction Objectives into Transportation Decision Making examines alternative methods that state departments of transportation and metropolitan planning organizations may use to manage greenhouse gas emissions from transportation.

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