Commuting in America 2013 

AASHTO: American Association of State Highway and Transportation Officials.

ACS: AMERICAN COMMUNITY SURVEY – is an ongoing survey of the Census Bureau that provides data every year. It is similar in content and structure to the “long form” of the decennial census which it replaced. It includes demographic questions asked of the American public, including the questions on work travel that are fundamental to this study.

APTA: The American Public Transportation Association.

ATUS: American Time Use Survey.

BLS: Bureau of Labor Statistics.

CARPOOL: A term currently used to describe any vehicle traveling to work with more than one person driving alone. In decades past, this term was used to describe a group of workers sharing the cost or driving chores on a regular basis.

CBD: CENTRAL BUSINESS DISTRICT. While not used by Census in their statistics, many states and metropolitan planning organizations continue to use the CBD as a critical geography for which examination of transportation is important to the economic health of the region. The term CBD used to be defined and supported by the Census Bureau but no longer is.

CENSUS: The US Bureau of the Census, or Census Bureau. This term is to be differentiated from a census, which is a complete count of a population, e.g., the decennial census. In this study the agency, the Census, is always shown with an initial capital letter, and the counting process with a lower case initial letter.

CENSUS GEOGRAPHY:  Census geographic structure, defined largely by Office of Management and Budget, has changed significantly in nomenclature and structure over the period of Commuting in America, making comparisons difficult from survey cycle to survey cycle. The definitions below, adapted from the more detailed Census definitions, seek to present these definitions in a way that makes them more coherent to the user who is not a specialist in this area. For additional insight into the technical definitions of these terms see:

CBSAS: CORE BASED STATISTICAL AREAS. The fundamental unit of metropolitan geography is now the CBSA defined as a core area containing a substantial population nucleus, together with adjacent communities having a high degree of economic and social integration with that core. The term “core based statistical area” became effective in 2003 and refers collectively to metropolitan statistical areas and micropolitan statistical areas. CBSA consist of the county or counties or equivalent entities associated with at least one core (urbanized area or urban cluster) of at least 10,000 population, plus adjacent counties having a high degree of social and economic integration with the core as measured through commuting ties with the counties associated with the core.

The Urbanized area or urban cluster identified above are identical in concept but are different in size now defined as:

UA: URBANIZED AREA. An urbanized area consists of densely developed territory that contains 50,000 or more people. The Census Bureau delineates UAs to provide a better separation of urban and rural territory, population, and housing in the vicinity of large places.

UCS: URBAN CLUSTERS. An urban cluster consists of densely developed territory that has at least 2,500 people but fewer than 50,000 people. The Census Bureau first introduced the UC concept for Census 2000 to provide a more consistent and accurate measure of urban population, housing, and territory throughout the United States, Puerto Rico, and the Island Areas.

The CBSA are grouped and described as:

METROPOLITAN STATISTICAL AREAS: Metropolitan statistical areas are CBSAs associated with at least one urbanized area that has a population of at least 50,000. The metropolitan statistical area comprises the central county or counties or equivalent entities containing the core, plus adjacent outlying counties having a high degree of social and economic integration with the central county or counties as measured through commuting.

MICROPOLITAN STATISTICAL AREAS: Metropolitan statistical areas are CBSAs associated with at least one urban cluster that has a population of at least 10,000 but less than 50,000. The micropolitan statistical area comprises the central county or counties or equivalent entities containing the core, plus adjacent outlying counties having a high degree of social and economic integration with the central county or counties as measured through commuting.

CSAS: COMBINED STATISTICAL AREAS. Combined statistical areas consist of two or more adjacent CBSAs that have substantial employment interchange. The CBSAs that combine to create a CSA retain separate identities within the larger CSA. Because CSAs represent groupings of metropolitan and/or micropolitan statistical areas, they should not be ranked or compared with individual metropolitan and micropolitan statistical areas.

PRINCIPAL CITIES: Principal cities of a CBSA now consist of multiple population and job centers distributed throughout the metro area. They include the largest incorporated place with a population of at least 10,000 in the CBSA, or if no incorporated place of at least 10,000 population is present in the CBSA, the largest incorporated place or census designated place (CDP) in the CBSA. Principal cities also include any additional incorporated place or CDP with a population of at least 250,000 or in which 100,000 or more persons work; any additional incorporated place or CDP with a population of at least 50,000 and in which the number of jobs meets or exceeds the number of employed residents; and any additional incorporated place or CDP with a population of at least 10,000 but less than 50,000 and at least one-third the population size of the largest place and in which the number of jobs meets or exceeds the number of employed residents. These principal cities are not differentiated between the central city of the metropolitan unit and other satellite cities making geographic specificity of the areas impossible to delineate.

CENSUS REGION: The states of the United States are grouped into four main regions for purposes of census data presentation. These four regions are further subdivided into nine divisions

West Midwest South Northeast
Washington North Dakota Texas Pennsylvania
Alaska South Dakota Oklahoma New York
Oregon Minnesota Arkansas New Jersey
California Iowa Louisiana Connecticut
Hawaii Nebraska Mississippi Rhode Island
Nevada Kansas Alabama Massachusetts
Idaho Missouri Georgia Vermont
Montana Wisconsin Florida New Hampshire
Wyoming Illinois Tennessee Maine
Utah Indiana Kentucky
Colorado Ohio South Carolina
New Mexico Michigan North Carolina
Arizona Virginia
West Virginia


CENSUS TRACT: A census-defined area of relatively homogeneous character within a metropolitan area circumscribing a population of about 4,000 inhabitants. Thus, tract areas vary in geographic size due to population density.

CENTRAL CITY: Generally, the central, incorporated, densely populated city around which a metropolitan area is structured. In the past, there were some cases where more than one central city existed inside a metropolitan area. Part of the Census changes in geographic definitions for 1990 and continued in 2000 included making any city with greater than 25,000 population within a metropolitan area a central city if it met certain other commuting criteria. This resulted in the development of a large number of new central cities within metropolitan areas. Recognizing that such cities were no longer central in character, the Census Bureau changed the name to Principal Cities for application with the 2010 census data. This does not differentiate the formerly central cities from other cities that were suburban in character.

CEX: Consumer Expenditure Survey.

CIA: Commuting in America.

CIVILIAN LABOR FORCE: Consists of those persons employed and those persons unemployed but seeking work, and only includes those who are not part of the armed forces.

CPS: Current Population Survey – primary source for labor force statistics for the population of the United States.

CTPP: Census Transportation Planning Products Program.

FHWA: Federal Highway Administration.

FTA: Federal Transit Administration.

GROUP QUARTERS POPULATION: The group quarters population is defined by the Census Bureau to include all people not living in households. Two general categories of people in group quarters are recognized: 1) the institutionalized population that includes people under formally authorized, super-vised care or custody in institutions (such as correctional institutions, nursing homes, and juvenile institutions) at the time of enumeration and 2) the non-institutionalized population that includes all people who live in group quarters other than institutions (such as college dormitories, military quarters, and group homes). It is the latter group that has work travel potential and is of interest in this study.

HOUSEHOLD: A group of persons sharing a separate housing unit, characterized by eating and sharing other activities together, as differentiated from persons living in group quarters (e.g., barracks, dormitories, etc.). Families constitute the majority of households. Single individuals living alone or unrelated persons sharing a housing unit also constitute households.

HPMS: Highway Performance Monitoring System.

HUD: U.S. Department of Housing and Urban Development.

IMMIGRANTS: As used here, includes foreign-born population that entered the United States. Persons born abroad of American parents are considered native born.

JOBS: In this study, the count of workers is sometimes used as a surrogate for the count of jobs at the work end of their journey to work. This is useful as an estimate only. Specifically, because multiple jobs are not counted in the census, workers are an under-estimate of jobs and, therefore, of commuting.

LABOR FORCE: That part of the non-institutional population over 16 that is working, temporarily absent from work, or actively seeking work. See Workers.

LABOR FORCE PARTICIPATION RATE: Defined by the Bureau of Labor Statistics as the labor force as a percent of the over-16 civilian non-institutional population. The definition therefore excludes those in the military and those in institutionalized settings such as correctional institutions, nursing homes, or juvenile institutions.

LEHD: Longitudinal Employment Household Dynamics – a Census produced data set based on administrative records.

MODE: In Census terms this is the means of transportation used to commute to work. Public transportation may be considered a mode, with bus, subway, or commuter rail as sub-modes, or each may be considered modes of travel in their own right. For this study, the census categories for identifying how people usually get to work are treated as separate modes. The census data do not permit identification of work trips using more than one mode (e.g., auto to train) and sometimes referred to as multimodal trips. In such cases, the mode used for most of the distance is used to describe the total trip. Walking is considered a mode only if it is the sole means of travel to work. The census also focuses on the “usual” mode during the referenced survey week and does not account for travel variations within the week for a given worker. The NHTS does count all modes used in the trip to work.

NCS: National Compensation Survey.

NHTS: NATIONAL HOUSEHOLD TRAVEL SURVEY. This is household based trip diary survey conducted by the FHWA/USDOT. It has been done in 1969, 1977, 1983, 1990, 1995, 2001 and 2009. Originally called the Nationwide Personal Transportation Survey, this survey has been conducted by the Federal Highway Administration with support from other units of the USDOT to obtain the daily trip patterns of the American public. It has been called the National Household Travel Survey (NHTS) since the 2001 cycle.


NCHRP: National Cooperative Highway Research Program.

NTD: National Transit Database.

ORIGIN-DESTINATION (O·D): A method of describing trips in terms of their starting and ending points. Generally, but not necessarily, for work trips the home is the origin, and the workplace the destination. However, students working after school, workers traveling to various client locations or construction work sites are examples of exceptions.

OMB: Office of Management and Budget.

PERSON TRIP: One trip made by one person. A trip is the one-way travel from an origin to a destination (usually a change of address), a visit to a neighbor, to the store, or to work. The return would be another trip.

PMT: PERSON MILES OF TRAVEL. Total person trips made multiplied by their lengths.

POV: PRIVATELY OPERATED VEHICLE. Also called privately owned vehicle; previously called an automobile, but with the advent of pick-up trucks, vans, etc., this more general term is employed.

PRINCIPAL CITIES: See Census Geography.

PUMS: PUBLIC USE MICRODATA SAMPLE. The Census Bureau has extracted a sample of 1% and 5% of all decennial census records with complete detail of the actual individual census forms so that researchers can examine detailed person and household information from the census. The smallest geographic units available are large enough to assure anonymity of the respondents. Detailed geographic identification is removed from the files so that individual privacy is protected. These files have been made available to substantially improve the utility of the data for research.

REVERSE COMMUTE: A term often used by transportation professionals to denote the travel of central city residents to suburban work locations in the opposite direction of the traditional main volume of traffic flow.

RURAL AREA: Rural encompasses all population, housing, and territory not included within an urban area. Parts of metropolitan areas may be rural. Nonmetropolitan areas are predominantly rural but also contain urban sections, nonmetropolitan urban units are now referred to as Micropolitan.

SIPP: Survey of Income and Program Participation.

STEM: Science, Technology, Engineering, and Mathematics.

SOV: SINGLE-OCCUPANT VEHICLE. A vehicle in which the driver is the only occupant. Also see VEHICLE OCCUPANCY.

SUBURB: In this study, the term suburb is used to describe the ring around the central city, the remainder of the metropolitan area, within various metropolitan definitions. This would make it equivalent to the census term metropolitan area outside a central city. With the advent of the principal cities concept, many of which are suburban in location, the concept of suburban is further muddled, reducing its analytical strength. This study in some specific cases seeks to differentiate areas suburban in character from the formerly defined central city.

TARP: Troubled Asset Relief Program.

TAZ: TRAFFIC ANALYSIS ZONE. A small area unit designated by metropolitan transportation planning agencies, defined by the configuration of the road system and homogeneous traffic patterns (i.e., a traffic-based neighborhood). Generally about one-third to one-quarter the size of a census tract, traffic zones do not have specific population characteristics but tend to be around 1,000 persons in population.

TDM: Transportation Demand Management.

TLH: TIME LEFT HOME. A data item developed first in the 1990 census. It identifies the time to the minute when the commuter left home for work. This information permits better analysis of traffic loadings around peak periods for local traffic and air quality analysis. The 2000 census provided the first opportunity for comparative trend analysis with this variable. This information is crucial to assessing system adequacy. Sometimes time arrived at work equaling TLH + travel time, is employed as a destination measure.

TRADITIONAL COMMUTE: The pattern of commuting from a suburb-like area outside the city to a down-town location.

TRANSIT MODES: The census employs a generic set of transit mode categories that include bus or trolley bus, streetcar or trolley car, subway or elevated railroad, and ferryboat. These categories seek to cover the full array of kinds of transit available in most areas. However, the technical names employed around the country for transit facilities and the popular names can vary tremendously, sometimes leading to confusion on the part of transit users. The terms Metro, the T, the L, etc., have become part of popular understanding in many areas. As a result, some unavoidable confusion arises as to how to correctly code one’s activities when answering census questions.

TRB: Transportation Research Board.

TRAVEL TIME: An estimate by the commuter of the time in minutes that it usually took to get from home to work in the week prior to the census. This data item was first collected in 1980. The census only collects work trip distance in time; the NHTS obtains both distances to work in time and distance in miles. It would be inappropriate to assume that total daily commute time would be twice the morning average given the significant variation in morning and evening travel.

TRIP END: Either end of a trip. Used to describe trips in terms of their common origins or destinations (e.g., in this study, all work trips with a destination in the suburbs).

USDOT: U. S. Department of Transportation.

VEHICLE OCCUPANCY: The number of occupants in a vehicle, including the driver. Generally, this figure is lower for work trips than for other trip purposes. A term often seen with vehicle occupancy is SOV for a single-occupant vehicle – a vehicle in which the driver is the only passenger. The term POV, meaning privately owned or operated vehicle, will also be seen when the emphasis is on a vehicle that is neither part of a public transportation system nor for hire.

VEHICLE TRIP: A trip made in a private vehicle.

VEHICLES: Between 1960 and 1980 data were collected in the census on automobiles available at occupied housing units. In 1980, for the first time, the census separately identified and counted vans and trucks of one-ton capacity or less in addition to the traditional count of automobiles. The 1990 census merged the two separate questions into one question using the term vehicles, without differentiating type. Present Census products follow that arrangement. Vehicles are counted if kept at home for use by members of the household. Therefore, company cars or leased vehicles available for use are included. Accordingly, the count does not conform with vehicles owned by the household, but rather means vehicles available to the household. This broader concept is more valid for the purposes of this study.

VMT: VEHICLE MILES OF TRAVEL. Vehicle trips made multiplied by their length. Two people in a vehicle going one mile generates one VMT and two PMTs.

WORK AT HOME: In the ACS, a person who, in the week prior to the survey, had the usual place of work in his/her residence is counted as working at home. Those who have variable work locations such as construction workers, or who periodically work at home, are not included in the work-at-home group. A popular new, related term that has come into vogue is tele-commuter, which refers to someone who has a regular workplace away from home, but works at home on an occasional basis (i.e., once or twice a week).

WORKERS: In the decennial census long form in the past and ACS, a person is defined as a worker if he or she worked full-or part-time during the week previous to the administering of the Census questionnaire. A worker is counted once regardless of the number of jobs held. Multiple jobs are not counted separately. Worker is not a term used typically by other employment statistical reporting activities.

WORKING AGE POPULATION: That part of the population of an age to be considered eligible for the labor force. Most definitions typically use the number of persons over 16, feeling that persons over 65 may well still be potential members of the workforce. As our population ages, this number will be increasingly misleading. It is felt that even now, but certainly in the future, the large numbers of those over 65 will cause misinterpretation of that statistic. In this study, the population between the ages of 16 and 65 is identified as the workforce age group. Although it is increasingly true that workers will be over 65, the age group from 16-65 is still a very useful estimator of the potential labor force age group. Where appropriate, workers over 65 are identified separately.