An Assessment of Data, Tools, and Metrics for Equity in Decisions About Surface Transportation Investments (2025)
Chapter: Executive Summary
Executive Summary
The U.S. surface transportation system has powered the nation’s economy and helped individuals and communities rise in social and economic wealth, but the system’s benefits and burdens are not shared equitably across people from all walks of life. In the past 20 years states and localities, reinforced by legislative requirements,1 have made concerted efforts to measure the transportation system’s physical and operational performance, whereas the performance of transportation investments in meeting the life needs of disadvantaged and underserved populations is seldom assessed.
In 2022, Congress directed the U.S. Department of Transportation (USDOT) to sponsor a consensus study by the National Academies of Sciences, Engineering, and Medicine (the National Academies)2 to advise on ways to further the use of metrics to inform choices about surface transportation programs and projects that will advance equity. This report is the product of an expert committee of researchers and practitioners convened to fulfill the request to identify promising metrics and analytical tools for decisions that will lead to safer and more reliable access to essential destinations for life outcomes and to consider resulting impacts on people’s health and well-being. The advice in this report is intended, in part, to inform a subsequent National Academies’ study called for in the legislation to pilot
___________________
1 Public Law 114-94. December 4, 2015. Fixing America’s Surface Transportation (FAST) Act; and its predecessor, Public Law 112-141. July 6, 2012. Moving Ahead for Progress in the 21st Century Act (MAP-21).
2 Public Law 117-103. March 15, 2022; see Division L, Title I, U.S. Department of Transportation, Office of the Secretary, Research and Technology.
test promising approaches to equity analysis under the auspices of the Transportation Research Board’s (TRB’s) Cooperative Research Program (CRP).
To inform its recommendations, the committee reviewed practices used by state governments and metropolitan planning organizations for transportation equity analysis with emphasis on outcomes stressed in the study charge—safe and reliable access to housing, employment, health care, and education, as well as health impacts and other environmental justice interests. The committee looked for innovative approaches that could be applied more widely to improve the state of practice in equity analysis. As directed by its charge, the committee consulted a preceding TRB report that advised on actions USDOT should take to elevate equity in its competitive grant programs, and that pointed to a high degree of variability in the capacity of states and localities to undertake equity analyses.3
The study committee’s recommendations, which are presented next, are applicable to states, local governments, regional planning organizations, tribes, and other organizations that receive federal aid for transportation projects.
RECOMMENDATIONS
Pilot Test Equity Metrics for Accessibility and Environmental Justice
RECOMMENDATION 1: The U.S. Department of Transportation and Congress should direct, and resource as needed, states, localities, regional planning organizations, and other recipients of federal surface transportation funds to pilot the use of equity metrics to inform transportation prioritization and investment decisions. The pilots should include equity metrics for access to destinations, and environmental justice, defined to include health, safety, and environmental burdens.
Access-to-destinations (i.e., accessibility) metrics should be measured using proximity-to-destinations indicators of two main types: cumulative opportunity indicators (the number of destination types, such as job opportunities and health care facilities, that can be accessed from a specific location within a travel time threshold for a specific transportation mode), and travel time opportunity indicators (travel time to a given, desirable location when using a range of available modes) that use “mobility” indicators, such as measures of travel time, congestion levels, or number of trips per
___________________
3 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.
day. Proximity and mobility indicators and metrics are commonly used and easy to create, but must be coupled with a destination (e.g., travel time to employment) for an indication of accessibility. Granular data about the location of destinations and available modal transportation networks, when combined with demographic information such as who is residing in the housing or using the different modes, can be used to analyze for disparities in access as experienced by populations of concern. These “proximity-to-opportunity” metrics provide a good starting point for further assessment and development.
More can be done to ensure equity in the distribution of transportation-related burdens through more consistent and regular environmental justice evaluations of long-range transportation plans and statewide plans. Environmental justice evaluations to measure burden based on proximity, such as to surface transportation crash hotspots and sources of noise and air pollution would be strengthened by a consistent practice of combining those geographic data with demographic information.
Pilot Test Equity Metrics for Transportation Insecurity
RECOMMENDATION 2: The U.S. Department of Transportation and Congress should provide resources to states, local jurisdictions, regional planning organizations, and other recipients of federal surface transportation funds to pilot test tools that directly measure transportation insecurity as it is experienced and related by people. The pilot should be designed to demonstrate how tools measuring transportation insecurity relate to other equity metrics, such as access to essential destinations.
The concept of measuring a person’s transportation insecurity has emerged from research on people living with poverty and facing food insecurity due to a lack of resources and options for obtaining safe and nutritious food. The U.S. Department of Agriculture (USDA) defines households as being food insecure and has an index to measure insecurity from least to most severe. Likewise, transportation insecurity denotes a lack of reliable and safe transportation options. People who are transportation insecure miss trips and skip essential activities, contributing to social and emotional isolation. They may rely on others for rides or be forced to accept unsafe travel.
Few tools and metrics are available to identify individuals who face transportation insecurity and for whom the transportation system is failing to meet their needs. A good example of a transportation insecurity measurement tool is the University of Michigan’s Transportation Security Index (TSI) modeled after USDA’s food security index. The TSI is derived from a survey of people responding to a series of questions. An advantage of such an index, which is designed to capture the experiences of people living
with transportation insecurity, is that transportation planners can identify areas with concentrations of people experiencing insecurity, provided that the survey is administered over a large enough population and geographic scope. A single index also has the advantage of implementation simplicity for jurisdictions evaluating and prioritizing their transportation investment strategies. Changes in the index over time and by location can be monitored to assess progress and enable more refined planning. Trends and patterns as indicated by the index can help policymakers at the state and federal levels gain a better understanding of how jurisdictions, as well as their own policies, are meeting the transportation needs of the disadvantaged. Although an index such as the TSI is a broad metric derived from a standardized set of questions, it provides a unique bottom-up approach that considers local conditions and needs to create an individual-level outcome metric that addresses limitations of existing approaches.
More testing and validation of indices of transportation security, such as the University of Michigan’s TSI, is needed, for instance, to determine the optimal form for scaled use by the federal, state, and regional governments and for coupling the index with other metrics of accessibility that convey the relationship between need and access.
Fund and Support the Widespread Use of Equity Metrics
RECOMMENDATION 3: The U.S. Department of Transportation and Congress should provide resources for states, local jurisdictions, regional planning organizations, and other recipients of federal surface transportation aid to measure access, transportation insecurity, and environmental justice outcomes of their transportation investments and plans using the metrics and tools that were successfully piloted.
States, localities, and regional planning organizations are likely to require added resources to fully integrate equity metrics into their transportation investment planning and prioritization processes that include additional staffing capacity and staff training to use opportunity metrics. Lower-resourced agencies will need assistance in establishing a new way to prioritize transportation projects and programs to better engage with disadvantaged communities. The need for resources is especially acute for measuring transportation insecurity due to the need for surveys or other qualitative methods targeted to the most disadvantaged. Some may need resources, training, or publicly available software tools for automating calculation of opportunity indicators by demographic group and by mode.
Advance Research on Transportation’s Role in Societal Outcomes
RECOMMENDATION 4: The U.S. Department of Transportation should fund sustained research to strengthen and expand understanding of existing, new, and emerging causal pathways from transportation investment to societal outcomes of critical importance.
Research that improves understanding of how transportation can affect the health, education, employment, and wealth generation outcomes of disadvantaged populations is essential for supporting the development of more insightful and useful metrics and tools for assessing equity and transportation. Because life outcomes associated with transportation have multiple causes that go beyond and intersect with transportation, an even deeper understanding is needed to specify causal connections between transportation investments and the well-being of the people and communities to further the use of metrics for planning and prioritization of transportation investments that advance equity. In this endeavor, transportation can learn from other fields that use evidence-based research to guide practice. Applying causal chain analysis used in health and safety research, as well as in other fields, to transportation can help identify root causes and the many layers of contributors to an identified need or desired outcome, and engage urban planners, engineers, and community members in identifying new and innovative solutions.
IMPLEMENTATION CONSIDERATIONS FOR AMERICAN INDIAN/ALASKA NATIVE PEOPLES AND TRIBAL GOVERNMENTS
Implementation of these recommendations requires special attention to tribal lands and American Indian/Alaska Native (AI/AN) peoples. Tribal governments whose relationship with the federal government is defined by both dependence and sovereignty need equity-related data, metrics, and tools that they can use to inform their own transportation decisions. Federal, state, and local governments also need better data, metrics, and tools for assessing the equity outcomes of their transportation decisions on tribal governments and AI/AN peoples living outside tribal lands.
Federal equity mapping tools are of limited use for planning the location of transportation projects, in part because their census tracts do not always align with tribal census tracts used by the Census Bureau to define tribal lands. Tribes struggle to access data in general, and they specifically lack access to high-resolution community and transportation infrastructure data. If they are to develop and use metrics for decision making, tribes will need assistance in obtaining the required data, and other distinct capacity constraints of tribes for undertaking equity analysis will need to be assessed.
SUGGESTIONS FOR PENDING PILOT TESTING
The advice in this report is intended, in part, to inform follow-on pilot testing of promising equity metrics and analytic tools to evaluate how they can be successfully implemented for common and sustained use. Sponsored by USDOT, the pilot tests are slated to be conducted by TRB’s CRP following the completion of this report. The purpose of the CRP work is to assess the potential for metrics and tools to be widely used. The committee believes that the pilot tests should be designed primarily for generalizability by evaluating metrics and tools that are sufficiently advanced and that are not conceptual or in early stages of development.
In considering candidates for the pilot testing, the committee concluded that the measurement of transportation insecurity to ascertain need should be a priority. Understanding need is an imperative and critical for implementing other equity metrics. The University of Michigan’s TSI is an example of an advanced tool for measuring transportation need that has been validated and has the potential for widespread use. Its short-form design allows it to be readily incorporated into existing surveys, while its longer-form version could potentially support deeper geography-specific assessments (e.g., at the census-tract level) of transportation need. Significantly, pilot tests of a transportation insecurity metric such as the TSI could be designed to improve understanding of how proximity to destinations (i.e., accessibility) relates to needs and to transportation investments.
Finally, an important observation of this report is that the baseline transportation and access conditions of many tribal lands and AI/AN communities are not well understood, for instance, on road systems and travel patterns. Pilot tests of transportation insecurity metrics are critically needed for tribal lands and AI/AN communities and should be included in the follow-on research, but they must be coupled with efforts to measure and understand these baseline conditions.
