Documentation
2010 Rural-Urban Commuting Area (RUCA) Codes
To determine a census tract, please go to the FFIEC Geocoding/Mapping System page and type in the address information.
Background
The rural-urban commuting area (RUCA) codes, a detailed and flexible scheme for delineating sub-county components of rural and urban areas, have been updated using data from the 2010 decennial census and the 2006-10 American Community Survey (ACS). RUCA codes are based on the same theoretical concepts used by the Office of Management and Budget (OMB) to define county-level metropolitan and micropolitan areas. We applied similar criteria to measures of population density, urbanization, and daily commuting to identify urban cores and adjacent territory that is economically integrated with those cores. We adopted OMB's metropolitan and micropolitan terminology to highlight the underlying connectedness between the two classification systems. However, the use of census tracts instead of counties as building blocks for RUCA codes provides a different and more detailed geographic pattern of urban and rural areas.
Census tracts are used because they are the smallest geographic building block for which commuting flow estimates are available from the U.S. Census. Tract-to-tract commuting flow files were constructed from ACS data as part of a special tabulation for the Department of Transportation—the Census Transportation Planning Package. To derive estimates for small geographic units such as census tracts, information collected annually from over 3.5 million housing units was combined across 5 years (2006-10). As with all survey data, ACS estimates are not exact because they are based on a sample. In general, the smaller the estimate, the larger the degree of uncertainty associated with it.
The classification contains 10 primary and 21 secondary codes. Few, if any, research or policy applications need the full set of codes. Rather, the system allows for the selective combination of codes to meet varying definitional needs.
Primary and Secondary RUCA Codes
The 10 whole numbers shown in Table 1 below refer to the primary, or single largest, commuting share. Metropolitan cores (code 1) are defined as census tract equivalents of urbanized areas. Micropolitan and small town cores (codes 4 and 7, respectively) are tract equivalents of urban clusters. Tracts are included in urban cores if more than 30 percent of their population is in the urbanized area or urban cluster.
High commuting (codes 2, 5, and 8) means that the largest commuting share was at least 30 percent to a metropolitan, micropolitan, or small town core. Many micropolitan and small town cores themselves (and even a few metropolitan cores) have high enough out-commuting to other cores to be coded 2, 5, or 8; typically these areas are not job centers themselves but serve as bedroom communities for a nearby, larger city. Low commuting (codes 3, 6, and 9) refers to cases where the single largest flow is to a core, but is less than 30 percent. These codes identify "influence areas" of metro, micropolitan, and small town cores, respectively, and are similar in concept to the "nonmetropolitan adjacent" codes found in other ERS classification schemes (Rural-Urban Continuum Codes, Urban Influence Codes). The last of the general classification codes (10) identifies rural tracts where the primary flow is local or to another rural tract.
| Code | Classification description |
|---|---|
| 1 | Metropolitan area core: primary flow within an urbanized area (UA) |
| 2 | Metropolitan area high commuting: primary flow 30% or more to a UA |
| 3 | Metropolitan area low commuting: primary flow 10% to 30% to a UA |
| 4 | Micropolitan area core: primary flow within an urban cluster of 10,000 to 49,999 (large UC) |
| 5 | Micropolitan high commuting: primary flow 30% or more to a large UC |
| 6 | Micropolitan low commuting: primary flow 10% to 30% to a large UC |
| 7 | Small town core: primary flow within an urban cluster of 2,500 to 9,999 (small UC) |
| 8 | Small town high commuting: primary flow 30% or more to a small UC |
| 9 | Small town low commuting: primary flow 10% to 30% to a small UC |
| 10 | Rural areas: primary flow to a tract outside a UA or UC |
| 99 | Not coded: Census tract has zero population and no rural-urban identifier information |
These 10 codes offer a relatively straightforward and complete delineation of metropolitan and nonmetropolitan areas based on the size and direction of primary commuting flows. However, secondary flows may indicate other connections among rural and urban places. Thus, the primary RUCA codes are further subdivided to identify areas where classifications overlap, based on the size and direction of the secondary, or second largest, commuting flow (table 2). For example, 1.1 and 2.1 codes identify areas where the primary flow is within or to a metropolitan core, but another 30 percent or more commute to a larger metropolitan core. Similarly, 10.1, 10.2, and 10.3 identify rural tracts for which the primary commuting share is local, but more than 30 percent also commute to a nearby metropolitan, micropolitan, or small town core, respectively.
| Code | Classification description |
|---|---|
| 1 Metropolitan area core: primary flow within an urbanized area (UA) | |
| 1.0 | No additional code |
| 1.1 | Secondary flow 30% to 50% to a larger UA |
| 2 Metropolitan area high commuting: primary flow 30% or more to a UA | |
| 2.0 | No additional code |
| 2.1 | Secondary flow 30% to 50% to a larger UA |
| 3 Metropolitan area low commuting: primary flow 10% to 30% to a UA | |
| 3.0 | No additional code |
| 4 Micropolitan area core: primary flow within an urban cluster of 10,000 to 49,999 (large UC) | |
| 4.0 | No additional code |
| 4.1 | Secondary flow 30% to 50% to a UA |
| 5 Micropolitan high commuting: primary flow 30% or more to a large UC | |
| 5.0 | No additional code |
| 5.1 | Secondary flow 30% to 50% to a UA |
| 6 Micropolitan low commuting: primary flow 10% to 30% to a large UC | |
| 6.0 | No additional code |
| 7 Small town core: primary flow within an urban cluster of 2,500 to 9,999 (small UC) | |
| 7.0 | No additional code |
| 7.1 | Secondary flow 30% to 50% to a UA |
| 7.2 | Secondary flow 30% to 50% to a large UC |
| 8 Small town high commuting: primary flow 30% or more to a small UC | |
| 8.0 | No additional code |
| 8.1 | Secondary flow 30% to 50% to a UA |
| 8.2 | Secondary flow 30% to 50% to a large UC |
| 9 Small town low commuting: primary flow 10% to 30% to a small UC | |
| 9.0 | No additional code |
| 10 Rural areas: primary flow to a tract outside a UA or UC | |
| 10.0 | No additional code |
| 10.1 | Secondary flow 30% to 50% to a UA |
| 10.2 | Secondary flow 30% to 50% to a large UC |
| 10.3 | Secondary flow 30% to 50% to a small UC |
| 99 Not coded: Census tract has zero population and no rural-urban identifier information | |
RUCA codes are many, but permit stricter or looser delimitation of metropolitan, micropolitan, and small town commuting areas. This classification scheme provides an alternative to county-based systems for situations where more detailed geographic analysis is feasible. It identifies areas of emerging urban influence and areas where urban-rural classifications overlap, thus providing an exhaustive system of statistical areas for the country.
A link to the ZIP code approximation of the 2010 RUCA codes is available on the Center for Rural Health website. It is based on a crosswalk between census tracts and ZIP code areas, not on a separate analysis of population and commuting data unique to the ZIP code geographic unit.
Learn more about the 2000 ZIP code approximation of the RUCA codes at the University of Washington.
This research was sponsored by ERS and the Federal Office of Rural Health Policy (HHS). For further information, see Morrill, Richard, John Cromartie, and Gary Hart. 1999. "Metropolitan, Urban, and Rural Commuting Areas: Toward a Better Depiction of the United States Settlement System." Urban Geography 20: 727-748.