Glossary of Terms

American Community Survey

The American Community Survey (ACS) is an ongoing statistical survey by the U.S. Census Bureau. It regularly gathers information previously contained only in the long form of the decennial census.

Annual GHG per Household

Greenhouse gas emissions from household auto use are calculated using the modeled values for Vehicle Miles Traveled, national average fuel efficiency (20.7 mpg), and an average emissions factor (0.438 metric tonnes of CO2 per mile). This per household measure divides the total block group emissions by the count of households.

Annual GHG per Acre

Greenhouse gas emissions from household auto use are calculated using the modeled values for Vehicle Miles Traveled, national average fuel efficiency (20.7 mpg), and an average emissions factor (0.438 metric tonnes of CO2 per mile). This per acre measure divides the total block group emissions by the total land acres in the block group.

Area Median Income

Area Median Income (AMI) is the median household income in the Core Based Statistical Area.

Auto Ownership Costs

Auto Ownership Costs, for the purposes of this research, have been defined as the cost of depreciation, finance charges, insurance, license, registration, and taxes (state fees) per auto. These costs are largely fixed, less determined by use, and therefore, a result of simply owning an automobile.

Auto Use Costs

Auto Use Costs, for the purposes of this research, have been defined as the cost of gas, maintenance, and repairs per mile. These costs are largely variable and therefore determined primarily based on the level of use of the automobile.

Autos per Household

Autos per Household is a model estimate of the average number of vehicles owned by households in a given Block Group.

Average Available Transit Trips per Week

Average Available Transit Trips per Week is the number of transit rides possible from a given block group (both within the Block Group and up to a ¼ mile from its boarder).

Average Block Size

Average Block Size, calculated in acres, is the average size of all the blocks making up a given Block Group. This factor has been included as a potential indicator of walkability in an area, with smaller blocks contributing to a more desirable walking environment.

Average Commuters per Household

Average Commuters per Household is calculated using the total workers 16 years and over who do not work at home from the American Community Survey. Because this variable includes workers not living in housing units (i.e. those living in group quarters), the ratio of total population in occupied housing units to total population was used to scale the count of commuters to better represent those living in households.

Average Household Size

Average Household Size reflects the value of total population in occupied housing units divided by the count of occupied housing units.

Average Monthly Housing Costs

Average Monthly Housing Costs are derived directly from the American Community Survey. Median Selected Monthly Owner Costs and Median Gross Rent are averaged and weighted by the ratio of owner- to renter-occupied housing units from the Tenure variable.

Average Regional Gas Price

Average regional gas prices were obtained for the year 2011 from the U.S. Energy Information Administration.

Block Group

A subdivision of a census tract, a Block Group is the smallest geographic unit for which the Census Bureau tabulates sample data. All data utilized in the H+T Index, unless otherwise noted, are calculated and modeled at the block group level.

Built Environment

The built environment refers to man-made (versus natural) resources and infrastructure designed to support human activity, such as buildings, roads, transit, parks, stores and other amenities.

Carbon Dioxide (CO2) Emissions

Carbon dioxide is generated as a by-product of the combustion of fossil fuels or the burning of vegetable matter, among other chemical processes. Here, we refer to the CO2 emissions resulting from private automobile use.

Compact Neighborhood Score

The Compact Neighborhood Score is an index that assesses the density and walkability of an area.

Core Based Statistical Area

Metropolitan and micropolitan statistical areas are geographic entities defined by the Office of Management and Budget (OMB) for use by federal statistical agencies in collecting, tabulating, and publishing national statistics. The term Core Based Statistical Area (CBSA) is a collective term for both metropolitan and micropolitan areas.

Cost Burden

A Cost Burden represents an expenditure as a percent of income.

Employment Access Index

Employment Access Index is a weighted measure developed by CNT to estimate both the quantity of and residents’ access to the jobs in a region. It is calculated using an inverse-square law to model total access to jobs in the metropolitan area by using the sum of the number of jobs divided by the square of the distance to those jobs.

Employment Mix Index (0-100)

The Employment Variation Index is based on employment type and looks at various industries and how they drive transportation costs.

Frequency of Service

Frequency of Service represents an estimate of the number of times a given transit route runs in a given amount of time. For this research, frequency of service has been estimated from either headway data provided by the transit agency or directly from route schedules. Route frequency is estimated as trips per week.

Fuel Efficiency

In reference to automobiles, a national average fuel efficiency figure of 21.6 mpg has been utilized.

Gasoline Expenses

Gasoline Expenses refer to the amount of money spent by a household on gasoline in a given period of time. These values are calculated using modeled vehicle miles traveled per household, reported gasoline prices, and an average fuel efficiency of 21.6 miles per gallon.

General Transit Feed Specification (GTFS)

General Transit Feed Specification (GTFS) defines a common format for transit schedules and associated geographic information. GTFS feeds allow transit agencies to publish their data and developers to write applications.

Gross Household Density

Gross Household Density is defined as total households per total land acres.

Housing Costs as a Percent of Household Income

Housing Costs as a percent of income has widely been utilized as a measure of affordability. Traditionally, a home is considered affordable when the costs consume no more than 30% of household income.

Housing + Transportation (H + T) Costs as a Percent of Household Income

H+T has been developed as a more complete measure of affordability beyond the standard method of assessing only Housing Costs. By taking into account both the cost of housing as well as the cost of transportation associated with the location of the home, H+T provides a more complete understanding of affordability. Dividing these costs by the representative income illustrates the Cost Burden placed on a Typical Household by H+T expenses. While housing alone is traditionally deemed affordable when consuming no more than 30% of income, CNT has defined an affordable range for H+T as the combined costs consuming no more than 45% of income.

Intersection Density

For each block group, the sum of all intersections (including those on the borders) is calculated and divided by the total land area of the block group.

Job Access Score

The Job Access Score in an index based on access to jobs and variety of employment types.

Jobs Accessible in 30 Minute Transit Ride

Jobs Accessible in 30 Minute Transit Ride is the count of jobs with the Transit Access Shed which is defined as the optimal area accessible from any block group within 30 minutes by public transportation.

Location Efficiency

Compact neighborhoods with walkable streets, access to jobs and transit, and a wide variety of stores and services have high location efficiency. They require less time, money and greenhouse gas emissions for residents to meet their everyday travel needs.

Median Gross Rent

Median Gross Rent is used directly from the American Community Survey and represents the median monthly costs for renters paying cash rent; gross rent includes rent plus utilities and fuels.

Median Household Income

Median Household Income includes the income of the householder and all other individuals 15 years old and over in the household, whether they are related to the householder or not and is obtained directly from the American Community Survey.

Median Selected Monthly Ownership Costs

Median Selected Monthly Owner Costs are used directly from the American Community Survey and represent the median monthly costs of owners with a mortgage. Ownership costs include mortgage payments, real estate taxes, various insurances, utilities, fuels, mobile home costs and condominium fees.

Metric Ton

A Metric Ton is a common international measurement for the quantity of greenhouse gas emissions. A metric ton is equal to 2205 lbs or 1.1 short tons.

National Typical Household

The National Typical Household assumes a household income of $53,046 (the national median household income), a national average household size of 2.63, and a national average number of commuters per household of 1.13.

Percent Owner Occupied Housing Units

Percent owner occupied housing units is obtained directly from the American Community Survey from the Tenure variable and represents the amount of owner occupied housing units as a share of all occupied housing units.

Percent Renter Occupied Housing Unit

Percent renter occupied housing units is used directly from the American Community Survey from the Tenure variable and represents the amount of renter occupied housing units as a share of all occupied housing units.

Percent Single Family Detached Households

Percent of households living in single family detached housing units obtained directly from the American Community Survey.

Region

For this research, region refers to the Office of Management and Budget (OMB) defined Core Based Statistical Areas (CBSAs).

Regional Household Intensity

Regional Household Intensity is a gravity measure of all the households in the region. It is calculated as the sum of all households not in a given block group weighted by the distance squared.

Regional Moderate Household

The Regional Moderate Household assumes a household income of 80% of the area median, the regional average household size, and the regional average commuters per household.

Regional Typical Household

The Regional Typical Household assumes a household income that is the median income for the region, the average household size for the region, and the average commuters per household for the region. An important aspect of the H+T Index is that transportation costs are modeled for the "typical" household in a region, or the household represented by these three values.

Transit

Transit here refers to fixed-route public transportation provided on a repetitive, set schedule along a specific route. Each fixed-route trip serves the same origins and destinations, such as rail and bus; unlike demand responsive and vanpool services.

Transit Access Score

The Transit Access Score is an overall transit index that looks at connectivity, access to land area and jobs, and frequency of service.

Transit Access Shed

The Transit Access Shed is defined as the optimal area accessible from any block group within 30 minutes by public transportation scaled by the Frequency of Service.

Transit Connectivity Index (0-100)

The Transit Connectivity Index was developed by CNT as a measure of fixed-route bus and rail (and other fixed-guideway modes such as ferry) service levels. The Transit Connectivity Index is based on the number of transit stops within walking distance for households in a given Block Group scaled by the Frequency of Service. Data is presented as an index from 0-100; zero being no access and 100 being the most access. This measure is not available to all metro areas because of data acquisition issues.

Transit Use Costs

Public transit costs represent the average household costs of transit at the block group level. These costs are based on figures obtained from the National Transit Database and allocated based on transit use.

Transportation Costs

Transportation Costs represent the total cost of household transportation. Here, transportation costs are defined as the sum of Auto Ownership Costs, Auto Use Costs, and Transit Use Costs.

Transportation Costs as a Percent of Household Income

Transportation Costs are calculated as the sum of Auto Ownership Costs, Auto Use Costs, and Transit Use Costs. Dividing these costs by the representative income illustrates the Cost Burden placed on a Typical Household by Transportation Costs.

Vehicle Miles Traveled (VMT)

Vehicle Miles Traveled represents the average annual auto travel by a household. This includes commute travel, but also all other daily auto trips.