Transportation Disadvantaged Census Tracts (Historically Disadvantaged Communities) Interim Definition Methodology
Consistent with OMB’s Interim Guidance for the Justice40 Initiative, DOT’s interim definition of DACs includes (a) certain qualifying census tracts, (b) any Tribal land, or (c) any territory or possession of the United States. DOT has provided a mapping tool to assist applicants in identifying whether a project is located in a Disadvantaged Community, available at Transportation Disadvantaged Census Tracts (arcgis.com). A shapefile of the geospatial data is available Transportation Disadvantaged Census Tracts shapefile (version 2 .0, posted 5/10/22).
The DOT interim definition for DACs was developed by an internal and external collaborative research process (see recordings from November 2021 public meetings). It includes data for 22 indicators collected at the census tract level and grouped into six (6) categories of transportation disadvantage. The numbers in parenthesis show how many indicators fall in that category:
- Transportation access disadvantage identifies communities and places that spend more, and take longer, to get where they need to go. (4)
- Health disadvantage identifies communities based on variables associated with adverse health outcomes, disability, as well as environmental exposures. (3)
- Environmental disadvantage identifies communities with disproportionately high levels of certain air pollutants and high potential presence of lead-based paint in housing units. (6)
- Economic disadvantage identifies areas and populations with high poverty, low wealth, lack of local jobs, low homeownership, low educational attainment, and high inequality. (7)
- Resilience disadvantage identifies communities vulnerable to hazards caused by climate change. (1)
- Equity disadvantage identifies communities with a with a high percentile of persons (age 5+) who speak English "less than well." (1)
To identify the census tracts that could be considered transportation disadvantaged, the DOT Justice40 team took five steps:
- For each census tract, the percentile value is calculated for each of the 22 indicators, where the 99th percentile represents the most disadvantaged.
- Within each category, the average percentile for each tract is calculated.
- For each category, a tract is assigned a value of one (1) if it is in the 50th percentile of disadvantage (percentile ranking average = .5 or higher) and zero (0) otherwise. For the resilience category only, a tract is assigned a value of one (1) is it is in the top 75th percentile of disadvantage (.75 or higher).
- The scores for each category are summed for each census tract, resulting in a score ranging from zero (0), not in the 50th percentile of disadvantage in any category, to six (6), ranking in the 50th percentile of disadvantage in each of the six categories.
- A census tract is considered transportation disadvantaged if it has a score of four (4) or higher, interpreted as ranking in the top 50% of the average scores in each category, where higher scores represent more disadvantage.
Underlying Indicators and Sources in DOT Definition of Disadvantaged Communities
| Variable | Description | Data Source |
| >30 min commute | Percent of total population with a drive time to employment greater than or equal to 30 minutes | (1) |
| No Vehicle | Percent of total population with no vehicle(s) available | (2) |
| Walkability | A composite index of economic and built environment characteristics representing the extent to which the location is not supportive to walking | (3) |
| Transportation Burden | Transportation Costs % Income for the Regional Typical Household | (1) + (6) |
| Population 65 and older | Percent of total population over age 64 | (2) |
| Uninsured | Percent of population without health insurance | (2) |
| Disability | Percent of the non-institutionalized population with any disability | (2) |
| Homes Built Before 1960 | Percent of housing units built before 1960 (lead paint indicator) | (4) |
| Diesel | EJ Index for Diesel particulate matter level in air | (4) |
| Cancer | EJ Index for Air toxics cancer risk | (4) |
| Traffic Proximity | EJ Index for Traffic proximity and volume | (4) |
| PM25 | EJ Index for PM2.5 level in air | (4) |
| Ozone | Ozone level in air | (4) |
| Less HS Education | Percent of total population, age 25 and older, whose reported education is short of a high school diploma Proportion of occupied housing units not occupied by property owners |
(2) |
| Renters | Proportion of occupied housing units not occupied by property owners | (1) |
| Unemployment | Percent of civilian labor force reported as unemployed | (2) |
| GINI Index | Endemic inequality | (7) |
| Low Income | Percent of total population reported at or below area median income | (2) |
| Poverty | Percent of population below Federal Poverty Level | (2) |
| Housing Costs | Housing Costs % Income for the Regional Typical Household | (1) |
| Climate Hazards | Expected annual loss of life, building value and agricultural value from 18 climate hazards | (5) |
| Linguistic Isolation | Percent of households (interpreted as individuals) in linguistic isolation | (2) |
Data Sources
- U.S. Census Bureau. American Community Survey (ACS) 5 Year Estimates 2015-2019. 2019.
- Center for Disease Control. Social Vulnerability Index (SVI) [Internet]. 2018 [cited 2021 Oct 20]. Available from: https://www.atsdr.cdc.gov/placeandhealth/svi/index.html
- EPA Smart Locations- Smart Location Mapping | US EPA
- U.S. Environmental Protection Agency. EJSCREEN: Environmental Justice Screening and Mapping Tool [Internet]. 2021 [cited 2021 May 5]. Available from: https://www.epa.gov/ejscreen
- U.S. Department of Homeland Security Federal Emergency Management Agency. National Risk Index [Internet]. 2021 [cited 2022 Jan 6]. Available from: https://hazards.fema.gov/nri/
- HUD Exchange 3.0 Location Affordability Index - HUD Exchange
- FEMA Resilience Analysis and Planning Tool (GINI Index) – FEMA.gov/RAPT
Last updated: Thursday, April 27, 2023