An Assessment of Data, Tools, and Metrics for Equity in Decisions About Surface Transportation Investments (2025)
Chapter: 1 Introduction
1
Introduction
The United States has one of the most comprehensive transportation systems in the world. It has powered the nation’s economy and helped individuals and communities rise in social and economic wealth. However, the rise has not been even across the nation; some groups of people have been systematically disadvantaged through policy and infrastructure investment decisions.1 Transportation is a public good and the level of investment required to maintain and improve transportation systems underscores the importance of state and federal governments in providing adequate infrastructure. Public-sector investments in transportation, much like those in education, health care, and social services, yield long-term economic benefits, including increased economic output, reduced prices, and raised incomes and profits.2 Equity is a straightforward concept that insists on the fair sharing of these societal benefits (and their burdens) through the just provision of transportation infrastructure. Equitable access to transportation options enables individuals, from all walks of life, to lead meaningful lives and take advantage of
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1 National Academies of Sciences, Engineering, and Medicine. 2024. Elevating Equity in Transportation Decision Making: Recommendations for Federal Competitive Grant Programs. Washington, DC: The National Academies Press. https://doi.org/10.17226/27439.
2 Bhatta, S. D., and M. P. Drennan. 2003. “The Economic Benefits of Public Investment in Transportation: A Review of Recent Literature.” Journal of Planning Education and Research 22(3):288–296; Shapiro, R. J., and K. A. Hassett. 2005. “Healthy Returns: The Economic Impact of Public Investment in Surface Transportation.” American Public Transportation Association. https://www.apta.com/wp-content/uploads/Resources/resources/reportsandpublications/Documents/healthy_returns.pdf. Accessed October 25, 2024.
life-enhancing opportunities.3 Addressing transportation equity is essential for promoting fairness and justice in society.4
It is well established that transportation infrastructure and policies can produce significant disparities among communities—often resulting in clear “winners” and “losers.” Consider, for example, that cities with well-developed public transportation systems, such as New York or Tokyo, often see substantial economic and social benefits. Well-developed urban transportation systems provide efficient, affordable access to jobs, education, and services and facilitate economic growth by increasing accessibility and reducing travel times.5 Additionally, areas near transit hubs typically experience an increase in property values due to improved accessibility and reduced travel costs.6 Conversely, some communities can bear a greater burden due to transportation investment patterns, both historical and current. Highway and arterial improvements can result in low-income and minority neighborhoods experiencing higher air and noise pollution burden with little improvement in transportation costs or access.7 Rural and low-income communities can experience limited transportation options, restricting the kinds of destinations that might improve health care or provide access to better jobs. Disparities in access to jobs, health care, and education help to perpetuate or exacerbate cycles of poverty and social exclusion.8
Applying an equity lens through which to view transportation policies and projects provides an opportunity to move from determining whether investment is simply shifting winners and losers to one that focuses on
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3 Sanchez, T. 2007. The Right to Transportation: Moving to Equity. New York: Routledge. https://doi.org/10.4324/9781351179607.
4 Bullard, R. D. 2003. “Addressing Urban Transportation Equity in the United States.” Fordham Urban Law Journal 31(5). https://ir.lawnet.fordham.edu/ulj/vol31/iss5/2. Accessed October 23, 2024.
5 Banister, D., and Y. Berechman. 2001. “Transport Investment and the Promotion of Economic Growth.” Journal of Transport Geography 9(3):209–218. https://doi.org/10.1016/S0966-6923(01)00013-8; Dubé, J., F. Des Rosiers, M. Thériault, and P. Dib. 2011. “Economic Impact of a Supply Change in Mass Transit in Urban Areas: A Canadian Example.” Transportation Research Part A: Policy and Practice 45(1):46–62. https://doi.org/10.1016/j.tra.2010.09.002; Glaeser, E. L., M. E. Kahn, and J. Rappaport. 2008. “Why Do the Poor Live in Cities? The Role of Public Transportation.” Journal of Urban Economics 63(1):1–24. https://doi.org/10.1016/j.jue.2006.12.004.
6 Debrezion, G., E. Pels, and P. Rietveld. 2007. “The Impact of Railway Stations on Residential and Commercial Property Value: A Meta-Analysis.” Journal of Real Estate Finance and Economics 35(2):161–180. https://doi.org/10.1007/s11146-007-9032-z.
7 Hartford, T. A. 2023. “The Not-So-Natural Disaster: Constructing African American Neighborhoods by Collapsing Interstate Highways.” Loyola Journal of Public Interest Law 25(1):128–162.
8 Blumenberg, E., and M. Manville. 2004. “Beyond the Spatial Mismatch: Welfare Recipients and Transportation Policy.” Journal of Planning Literature 19(2):182–205. https://doi.org/10.1177/0885412204269103.
benefiting those most in need. As Chapter 2 describes, there are different definitions and ways of thinking about equity, and different situations call for different approaches depending on what is trying to be achieved. What is important to understand, however, is that when equity is a goal, the project or policy solution may not always be the most economically efficient; deciding whether and how to make this trade-off between efficiency and equity is a choice that requires equity metrics. In short, attention to equity helps to identify and/or further highlight where safety or access must be improved, and where there is a need to reduce or remove challenges or barriers to destinations that are fundamental to individual and societal well-being.
EXTENDING PERFORMANCE-BASED PLANNING
In 2012, Congress authorized the Moving Ahead for Progress in the 21st Century Act (MAP-21)9 governing federal surface transportation spending. The passage of MAP-21 increased emphasis on performance-based planning. State departments of transportation (DOTs) were required to align their transportation investments and policies with stated performance outcomes. Performance-based planning meant setting measurable goals, monitoring progress, and making informed decisions to achieve specific targets. As a result of this policy imperative, DOTs implemented monitoring and reporting systems to meet the MAP-21 mandates. These systems helped DOTs track progress and report on performance to the public, elected officials, and federal agencies. For most states, the benefits of implementing performance-based planning are a more transparent framework for decision making, closer ties between fund use and outcomes, more informed decision making, and greater stakeholder involvement, which helps to ensure that transportation plans reflect the needs and priorities of the community.10
Recent federal initiatives are targeted at advancing equity as a metric for evaluating federally funded projects. These include the Bipartisan Infrastructure Law (Infrastructure Investment and Jobs Act), which was signed into law in November 2021. This law mandates investments in public transit, roads, bridges, and rail systems with a focus on underserved communities, specifically improving access to transportation for people with disabilities, low-income communities, and minority groups. The U.S.
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9 Public Law 112-141. July 6, 2012.
10 Cambridge Systematic, Inc. 2010. “Report on a National Forum on Performance-Based Transportation Planning and Programming.” Prepared for National Cooperative Highway Research Program; Neumann, L. A., and M. J. Markow. 2004. “Performance-Based Planning and Asset Management.” Public Works Management & Policy 8(3):156–161. https://doi.org/10.1177/1087724X03259474.
Department of Transportation (USDOT) has been actively involved in this effort, focusing on equity in transportation infrastructure and services under the assumption that transportation agencies have the responsibility to ensure that all people have access to transportation that can meet their life needs and any single population should not experience disproportionate burdens.
Most state DOTs and metropolitan planning organizations (MPOs) do not have even basic equity analysis as part of their standard project or program prioritization. A 2022 survey examining the use of equity across all funding sources11 found that only three of the state DOTs (6%) and 20% of MPOs that responded to the survey included a quantitative equity screening component in their State Transportation Improvement Program or the transportation improvement plan (TIP) planning and programming processes.12 Forty percent of state DOTs used a quantitative screening for at least one funding source. Less than half of state DOTs and MPOs responding reported having equity policies or processes required by state or local legislation. The leading equity measures for state DOTs are enhanced communication with disparate communities and avoiding disparate impacts from plans, programs, and projects. Talking to communities is not sufficient for achieving equity, however; equity measures must be part of the actual selection and prioritization criteria. For MPOs, the leading indicators are ensuring that an equitable distribution of benefits resulting from plans, programs, and projects accrues to underserved communities and avoiding disparate impacts from plans, programs, and projects. These findings are consistent with a review of how the 40 largest MPOs integrate transportation equity into TIP project prioritization.13 In that review, nearly 50% of MPOs assessed equity, relying on proximity of transportation investments to communities of concern as their equity measure. As presented in this report, proximity to investments does not capture whether safe and reliable access to critical destinations is also enhanced. Many agencies regularly measure transportation project-specific outcomes such as reduced crashes or a decrease in congestion, but far fewer seem to include equity in their decision making.
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11 USDOT, Volpe National Transportation System Center. 2023. “2022 Survey of Equity Practices in the Transportation Planning Process.” https://www.transportation.gov/sites/dot.gov/files/2023-11/Summary%20of%202022%20Equity%20in%20the%20Transportation%20Planning%20Process_FINAL.pdf. Accessed November 24, 2024.
12 Survey findings are based on responses from 157 transportation management association-serving MPOs, 127 small MPOs, and 35 state DOTs.
13 Krapp, A., J. Barajas, and A. Wennink. 2021. “Equity-Oriented Criteria for Project Prioritization in Regional Transportation Planning.” Transportation Research Record 2675(9). https://doi.org/10.1177/03611981211001072.
The key performance measures reported under the Fixing America’s Surface Transportation (FAST) Act enacted in 2015,14 and its predecessor, MAP-21, broadly cover the areas of safety, pavement condition and travel time reliability, freight movement, congestion mitigation and air quality, and transit assets. The metrics used to evaluate progress in each area are noted in Box 1-1. Another set of performance measures applies to public transit agencies, as required in Public Transit Agency Safety Plans regulation.15 State DOTs and MPOs have made concerted efforts to collect data and improve decision making in part because of the federal mandates. Over the past 20 years, transportation planning and project prioritization have evolved to include increased collaboration between states and MPOs and data collection to improve decision making. The committee is energized that the next stage in assessment is measuring the equity effects of transportation improvements. This evolution will require a shift in focus from addressing only the performance aspects of new investments to reducing travel burden, taking a more people-centered perspective and placing more emphasis on accountability for achieving equitable outcomes.
STUDY ORIGINS AND CHARGE
This study is the second part of a three-phase effort. Phase 1 began in 2021, when the Transportation Research Board’s Executive Committee decided to sponsor a consensus study (co-sponsored with USDOT) that would provide recommendations to USDOT on how to best elevate equity in the transportation decision-making process, specifically those associated with USDOT’s competitive grants program. In its report, the Phase 1 study committee made several critical recommendations for USDOT to act upon, including eliminating barriers to participation in the competitive grants programs; developing a set of equity principles to guide each of the competitive grant programs to a more integrated, transparent, and consistent approach to equity considerations; prioritizing community-focused projects and prioritizing equity benefits; including equity in the post-award evaluation process; and supporting capacity building of underresourced applicants to the competitive grants program.16
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14 Public Law 114-94. December 4, 2015.
15 Federal Transit Administration. April 2024. National Public Transportation Safety Plan (pp. 12–14). https://www.transit.dot.gov/sites/fta.dot.gov/files/2024-04/National-Safety-Plan-04-05-2024.pdf; 49 CFR Part 673 [Docket No. FTA-2023-0007], https://www.transit.dot.gov/sites/fta.dot.gov/files/2024-04/PTASP-Final-Rule-2024-04-09_0.pdf. Accessed November 24, 2024.
16 National Academies of Sciences, Engineering, and Medicine. 2024. Elevating Equity in Transportation Decision Making: Recommendations for Federal Competitive Grant Programs. Washington, DC: The National Academies Press. https://doi.org/10.17226/27439.
BOX 1-1
Performance Measures Required by Federal Law (FAST and MAP-21)a
Safety
- Number of Fatalities: Total number of fatalities on all public roads.
- Rate of Fatalities: Rate of fatalities per 100 million vehicle miles traveled (VMT).
- Number of Serious Injuries: Total number of serious injuries on all public roads.
- Rate of Serious Injuries: Rate of serious injuries per 100 million VMT.
- Number of Non-Motorized Fatalities and Non-Motorized Serious Injuries: Total number of fatalities and serious injuries involving pedestrians and bicyclists.
Infrastructure Condition
- Pavement Condition: Percentage of pavements on the Interstate System and the non–Interstate National Highway System (NHS) in good and poor condition.
- Bridge Condition: Percentage of NHS bridges classified as in good condition and poor condition.
System Performance
- Travel Time Reliability: Percentage of person-miles traveled on the Interstate and the non-Interstate NHS that are reliable.
- Truck Travel Time Reliability (TTTR) Index: Reliability index for truck travel times on the Interstate System.
- Peak Hour Excessive Delay (PHED) Per Capita: Annual hours of peak hour excessive delay per capita.
- Non-Single Occupancy Vehicle (Non-SOV) Travel: Percentage of non-SOV travel, including carpool, public transit, bike, or walk.
- Total Emissions Reductions: Total emissions reduction in areas designated as nonattainment or maintenance for ozone, carbon monoxide, or particulate matter.
Transit Asset Management
- Rolling Stock: Percentage of revenue vehicles (by type) that exceed the Useful Life Benchmark (ULB).
- Equipment: Percentage of non-revenue service vehicles (by type) that exceed the ULB.
- Facilities: Percentage of facilities (by group) rated under 3.0 on the Transit Economic Requirements Model (TERM) Scale.
- Infrastructure: Percentage of track segments (by mode) with performance restrictions.
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a National Performance Management Measures; Assessing Performance of the National Highway System, Freight Movement on the Interstate System, and Congestion Mitigation and Air Quality Improvement Program. Federal Register, January 18, 2017, Document 2017-00681 (82 FR 5970). https://www.federalregister.gov/documents/2017/01/18/2017-00681/national-performance-management-measures-assessing-performance-of-the-national-highway-system; for “Transit Asset Management” performance measures, see Federal Transit Administration, Performance Management, https://www.transit.dot.gov/PerformanceManagement#Performance%20Measures. Accessed October 23, 2024.
Phase 2, this study, is the result of congressional direction in the Consolidated Appropriations Act of 2022.17 Congress directed USDOT to sponsor a consensus study to identify the opportunities and challenges associated with the equity data, metrics, and methods used at all levels of governance. The study committee was charged to focus on surface transportation projects, with emphasis on those using federal formula transportation funds. This study will be followed by a Phase 3 research study to pilot test and evaluate the identified data, metrics, and methods.
The statement of task for this Phase 2 study committee, developed in cooperation with the USDOT Office of the Assistant Secretary for Research and Technology, who sponsored the study, is as follows in Box 1-2. The main goals of this study are to identify and advise on opportunities for state, local, and tribal governments to use data, metrics, and analytic methods for measuring and assessing the effectiveness of surface transportation projects in addressing the transportation challenges and barriers faced by historically disadvantaged and underserved communities, areas of persistent poverty, and public transportation–dependent populations. Specifically, the study committee was asked to consider data and metrics related to safe and reliable access to housing, employment, health care, education, and essential services, as well as data and metrics for assessing equity about health impacts and other environmental justice interests. The study committee was charged with three primary tasks:
- Identify and analyze existing data and metrics to establish a baseline of currently available means for assessing and measuring outcomes from surface transportation projects;
- Identify opportunities to improve data, the use of such data to improve metrics, and how such metrics could be applied to make more informed decisions in the planning process for surface transportation projects; and
- Consider new and innovative sources of data, analytic methods, and modeling for using such data and metrics in the transportation planning and decision-making process.
It is important to understand that routinely using equity metrics in transportation decision making is a paradigm shift in which equity analysis is applied in partnership with performance-based decision making. That is, decisions on transportation investments would, in this paradigm, use both an equity lens and a performance lens. The equity lens helps to ensure that transportation investments align with other societal priorities, including,
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17 Public Law 117-103. March 15, 2022; see Division L, Title I, U.S. Department of Transportation, Office of the Secretary, Research and Technology.
BOX 1-2
Statement of Task
Data, Metrics, and Analytic Methods for Assessing Equity Impacts of Surface Transportation Investments: Phase 2 Study to Support State and Local Decision Making
The study committee will identify and advise on opportunities for state, local, and tribal governments to use data, metrics, and analytic methods for measuring and assessing the effectiveness of surface transportation projects in addressing the transportation challenges and barriers faced by historically disadvantaged and underserved communities, areas of persistent poverty, and public transportation–dependent populations. The study will consider data and metrics related to safe and reliable access to housing, employment, health care, education, and essential services, as well as data and metrics for assessing equity with regard to health impacts and other environmental justice interests. The study will (1) identify and analyze existing data and metrics to establish a baseline of currently available means for assessing and measuring outcomes from surface transportation projects; (2) identify opportunities to improve data, the use of such data to improve metrics, and how such metrics could be applied to make more informed decisions in the planning process for surface transportation projects; and (3) consider new and innovative sources of data, analytic methods, and modeling for using such data and metrics in the transportation planning and decision-making process.
On the basis of its review and assessments, the committee will advise on the most promising methodological approaches and requisite data for analyzing equity impacts from surface transportation projects, giving particular attention to projects that use federal formula transportation funds. The study will consider the findings and recommendations of the National Academies study on “Data, Metrics, and Analytic Methods for Assessing Equity Impacts of Surface Transportation Funding Programs (TRB-CAAS-21-03).” That study, which is underway, will identify data sources, metrics, and analytic methods that the U.S. Department of Transportation can use to assess the equity impacts of projects that are candidates for federal aid through its discretionary surface transportation funding programs.
It is expected that the results of this Phase 2 study will inform a follow-on (Phase 3) research project to develop and pilot test analytic tools and methods for states, local governments, metropolitan planning organizations, and tribal governments to use in performing equity analyses on the existing and planned surface transportation investments. This follow-on project, which would not be a consensus study, is proposed in a separate prospectus from the Transportation Research Board’s Cooperative Research Program.
for example, better access to educational or employment opportunities or a reduction of challenges and barriers to accessing adequate health facilities. The committee recognizes that reducing barriers and increasing opportunities can be achieved in many ways, ranging from better transportation investments to more effectively using wireless strategies and moving important destinations closer to communities and people in need. In some cases, combinations of strategies may be deployed, such as expanding transit access to disadvantaged communities and coupling this expansion with lowered transit fares to increase affordability. While recognizing that approaches to increasing equity may be widely varied depending on the context, the statement of task asks the committee to advise on “what” should be measured, not “how” to achieve outcomes. To move from prioritizing transportation investments based on physical performance criteria to a system inclusive of equity metrics, changes will be needed to procedures and administrative rules, a matter that is beyond this committee’s purview. Institutions must have the will (or mandate) to follow recommendations for considering equity, as noted in the Phase 1 study report.
Finally, like the Phase 1 study committee, this committee acknowledges that this study does not address all challenges presented by the past. There is a long history of prioritizing transportation investments that favor certain geographies and/or populations. This, coupled with segregation practices such as redlining, has created structural barriers. While including equity considerations in future analyses of transportation investments should help to overcome some of these barriers, many structural challenges will remain. The study task and work of this committee do not suggest that equity is sufficient as the only metric in assessing transportation investments. An equity metric helps to ensure that everyone has an equally safe and useful transportation system by helping to mitigate current inequities with informed strategies.
COMMITTEE SCOPE AND APPROACH
Committee members welcomed the opportunity to expand thinking about equity metrics, because as researchers and practitioners they recognized that transportation has deep and far-reaching connections to societal and individual well-being. In addressing its task, the committee collected information on the ways local and state governments currently use metrics for assessing transportation equity. The committee also reviewed new and innovative approaches that are being used by some state DOTs and regional organizations to integrate equity considerations in decisions about transportation programs and projects. As committee members deliberated over the course of their work, they were unified in their assessment that existing equity metrics could be successfully deployed now at all levels of governance given sufficient resources and motivation. Further, it was clear to members that,
with the addition of pilot testing, advanced metrics could usher in a new means for better aligning transportation investments with transportation need as well as broadening the types of investment strategies to address the challenges and barriers to life-sustaining and life-enhancing destinations.
The study committee was asked to focus on evaluating equity metrics, both current and possible, for surface transportation, which uses a formula-based funding allocation. Specifically, funds are allocated to states and local governments based on specific formulas set by legislation. These formulas consider various factors, such as population, road mileage, and other transportation-related data, to determine the distribution of funds. There are seven key programs within the formula-based funding, including the Federal-Aid Highway Program, which uses lane miles, vehicle miles traveled, and population to allocate federal funds; the National Highway Performance Program, which allocates based on the extent and condition of the National Highway System; the Surface Transportation Block Grant program, which uses population, lane miles, and the cost to maintain infrastructure; the Highway Safety Improvement Program, which uses factors such as the number of fatalities and serious injuries, road miles, and vehicle miles traveled; the Congestion Mitigation and Air Quality Improvement Program, where allocation is based on population and air quality measures; the Transportation Alternatives Set-Aside, which uses population, among other factors; and finally, the Federal Transit Administration Programs, where allocation takes into account factors like population, transit service levels, and passenger miles. The allocation formulas are periodically reviewed and adjusted through transportation authorization bills, such as the Infrastructure Investment and Jobs Act, to ensure they reflect current transportation needs and priorities. States and local governments then use these funds to plan, construct, maintain, and improve their transportation systems.
The study committee was also asked in the statement of task to pay specific attention to the challenges and barriers experienced by historically disadvantaged and underserved populations, areas of persistent poverty, and those dependent on public transportation with respect to safe and reliable access to housing, employment, health care, education, and essential services. Clearly, many people fall into two or more of these population categories. Moreover, many definitions exist for the same population. Take, for example, areas of persistent poverty. Federal definitions of persistent poverty usually connote areas where a significant portion of the population has been living below the poverty line for an extended period, but these definitions and criteria can vary slightly depending on the agency or the decision-making context.
The U.S. Department of Agriculture (USDA) defines a persistent poverty county as one where 20% or more of the population has lived in poverty for
the past 30 years, based on census data,18 while the Community Development Financial Institutions (CDFI) Fund within the U.S. Department of the Treasury identifies persistent poverty counties as those with a poverty rate of at least 20% in the 1990, 2000, and 2010 decennial censuses. USDOT defines “persistent poverty” consistent with the USDA definition. The agency uses this definition to prioritize funding and support for transportation projects that can help alleviate poverty and improve accessibility in these areas. The study committee found that individual MPOs and state DOTs have in some cases deployed their own definitions of historically disadvantaged and underserved populations, areas of persistent poverty, and those dependent on public transportation. The committee acknowledges these differences but did not weigh in on which to use. Different definitions may be applicable in different settings. It will be important in equity analysis to carefully assess the populations of interest, which may extend beyond the federally identified priority populations.19
The committee began its work by meeting with USDOT officials to better understand their interest in the study and proceeded to gather information from experts noted in this report’s Acknowledgments and Preface on topics that included current practices used to assess equity and inform decisions by state departments of transportation and metropolitan planning organizations; equity outcomes education, health, housing, and studies of economic opportunity; research on how transportation affects education, health, housing, and economic opportunity outcomes; ways of defining the populations of interest including people in “areas of persistent poverty” or who are “historically disadvantaged”; methods for measuring transportation experiences; and community-informed approaches to understanding transportation needs.
The committee recognized early in its deliberations that identifying metrics for assessing transportation performance with equity outcomes in mind called for an examination of the role of transportation in achieving better societal outcomes. The committee used a causal chain approach20 to help understand the role of transportation investments, and by default the role of their metrics, in improving societal outcomes. The causal chain
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18 USDA, Economic Research Service. “Poverty Area Measures—Descriptions and Maps.” https://www.ers.usda.gov/data-products/poverty-area-measures/descriptions-and-maps. Accessed January 11, 2025.
19 For in depth discussion of population definition issues, see National Academies of Sciences, Engineering, and Medicine. 2024. Constructing Valid Geospatial Tools for Environmental Justice. Washington, DC: The National Academies Press. https://doi.org/10.17226/27317.
20 Elvik, R. 2003. “Assessing the Validity of Road Safety Evaluation Studies by Analysing Causal Chains.” Accident Analysis & Prevention 35(5):741–748; Joffe, M., and J. Mindell. 2006. “Complex Causal Process Diagrams for Analyzing the Health Impacts of Policy Interventions.” American Journal of Public Health 96(3):473–479.
approach has been used in health research to articulate and understand the pathways through which exposure affects an outcome.21 This approach involves identifying and mapping out a series of intermediary steps or events that connect an initial cause (such as a risk factor) to its final effect (such as a health outcome). Often, intermediary variables mediate the relationship between the initial exposure (or a base condition) and a final outcome. For example, smoking (initial exposure) leads to tar accumulation in the lungs (intermediary variable), which causes cellular mutations (another intermediary variable), eventually leading to lung cancer (final outcome).
Following the causal chain approach, the committee observed that not every transportation project leads to direct improvements in societal outcomes. Transportation is a necessary but insufficient part of improving individual outcomes. The selection of metrics for assessing the effectiveness of transportation requires consideration of how benefits and burdens resulting from transportation intersect with the challenges and barriers of the broader built environment, which are affected by decisions about social and economic development outside of transportation projects.
In its work, the committee found that equity metrics and analytical tools are available and sometimes being used, but with significant limitations. It is important to be cognizant of some of the limitations that the committee observed. For example, demographic thresholds ignore the intersectional issues underlying equity. That is, for example, someone who both uses a wheelchair and is poor may experience greater transportation challenges relative to someone who uses a wheelchair but is not poor; without the insights that an intersectional view provides it is difficult to achieve a more equitable outcome. Many of the metrics in use also do not capture need, which requires a better understanding of how different communities define their transportation needs, which are based on lived experiences. In most cases, the committee observed that existing metrics are not aligned with a societal outcome. As noted earlier and throughout this report, transportation is only one part of improving critical societal outcomes (e.g., transportation alone will not improve education), and making this alignment will take deliberation and careful measurement over time.
While the report points to a number of key characteristics of metrics that are useful to decision making (see Chapter 3), the committee was not asked to examine the transportation planning and prioritization processes, or to provide recommendations on how to use equity metrics in decision making. There are multiple factors that can warrant consideration and exert influence on transportation investment decisions in different contexts. These are complex subjects that would require separate study.
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21 Greenland, S., J. Pearl, and J. M. Robins. 1999. “Causal Diagrams for Epidemiologic Research.” Epidemiology 10(1):37–48.
REPORT ORGANIZATION
The remainder of this report is organized into four chapters as follows.
Chapter 2 argues that transportation equity is best understood and measured with awareness of transportation’s role within larger societal systems. The chapter offers a causal chain analysis framework for understanding the causal pathways through which transportation investments may affect societal outcomes amid other nontransportation influences on these outcomes. The chapter summarizes literature on the contribution of transportation to societal outcomes in domains of life important to equity. This evidence base can serve as a resource for identifying indicators and metrics for equity analysis, and for a deeper understanding of points in the causal chains where transportation investments can be targeted. The chapter also defines key terms used in subsequent chapters.
Chapter 3 summarizes current practices, including indicators and metrics, used to assess equity by state departments of transportation and regional and local governments. The chapter considers limitations of federal tools and data for tribes and American Indian and Alaska Native individuals. The chapter also summarizes key characteristics of indicators and metrics that support their utility for decisions about transportation projects and programs.
Chapter 4 considers new and innovative approaches for advancing equity assessment in three areas: proximity to destinations as a measure of accessibility, transportation insecurity as a measure of transportation need, and environmental justice concerns, including disparities in health and safety.
Chapter 5 presents the committee’s recommendations and suggestions for piloting equity metrics and supporting their widespread adoption to inform transportation decisions by states, localities, regional planning organizations, tribes, and other recipients of federal surface transportation funds.
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