Housing + Transportation Affordability Index (H+T Index)
The H+T Index measures the affordability of housing by including transportation costs at a home’s location to better reflect the true cost of households’ location choices. 15 percent of household income is considered to be an attainable goal for transportation affordability while 30 percent be the housing affordability standard, adding up to the affordability defined as combined housing and transportation costs consuming no more than 45 percent of household income. Index values are obtained from the Center for Neighborhood Technology (CNT), 2022.
The table belows shows the housing and transportation cost as a percentage of household income for a regional typical household, i.e., a household earning the median income for the region, with the average household size for the region, and the average number of commuters per household for the region.
Note: Values other than census tract- or county-level are household-weighted averages.
Source
Source Description
The Center for Neighborhood Technology’s Housing + Transportation Affordability Index (H+T Index) is an innovative tool that measures the true affordability of housing by calculating the transportation costs associated with a home’s location. Planners, lenders, and most consumers traditionally consider housing affordable if the cost is 30 percent or less of household income. The H+T Index proposes expanding the definition of housing affordability to include transportation costs at a home’s location to better reflect the true cost of households’ location choices. Based on research in metro areas ranging from large cities with extensive transit to small metro areas with extremely limited transit options, CNT has found 15 percent of income to be an attainable goal for transportation affordability. By combining this 15 percent level with the 30 percent housing affordability standard, the H+T Index recommends a new view of affordability defined as combined housing and transportation costs consuming no more than 45 percent of household income.
Methodology
The H+T Index was constructed using the measured housing cost and modeled transportation cost. The housing cost are obtained from the American Community Survey 5-year Estimate (2019 ACS) using the selected monthly ownership cost and the gross rent and combines each using the relative number of owner occupied households and renting households. The transportation model estimates three dependent variables (auto ownership, auto use, and transit use) as functions of 17 independent variables:
- median household income
- average household size
- average commuters per household
- gross household density
- household intensity
- fraction of single family detached housing
- single family detached housing intensity
- fraction of rental housing units
- rental housing intensity
- employment intensity
- employment mix index
- block size
- bus transit connectivity index
- other (non-bus) transit connectivity index
- total available transit trips per week at peak times
- area of transit access shed
- jobs within the transit access shed
To focus on the built environment’s influence on transportation costs, the independent household variables (income, household size, and commuters per household) are set at fixed values to control for any variation they might cause. By establishing and running the model for a control household any variation observed in transportation costs is due to place and location, not household characteristics.
For more information about the H+T Affordability Index, please go to the H+T Index website or check the methodology document.
Data Breakouts Available
- Transportation Costs % Income
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