Subcommittee on Census Data For Transportation Planning

Proposed NCHRP Study

Use of Census American Community Survey Data in Transportation Planning

The Bureau of the Census is planning to replace the traditional decennial census "long form" with a continuous data collection program entitled the American Community Survey (ACS). During the 1999-2001 time period the Bureau of the Census will collect American Community Survey data in approximately 31 comparison sites in the U.S. The full implementation of the ACS will begin in 2003.

Demographers and transportation planners at the state, metropolitan and local levels need census data for socio-economic benchmarking and in journey-to-work analyses. Much of the data used by transportation planners is derived from the traditional census long form. The ACS will be very consistent in terms of survey content, but data will be collected continuously throughout the years and the decade, rather than April 1st of the census year.

Planners will need to transition from a once-a-decade analysis paradigm to a continuous measurement paradigm. To do this, planners need guidance in analyzing the statistical characteristics of American Community Survey data for large areas (e.g., counties, places) and small areas (neighborhoods and travel analysis zones) on a time-series basis.  For example, the standard errors associated with the American Community Survey may be significantly larger than the standard errors with traditional census long form data. The analyst will need to understand and explain these statistical errors to decision-makers, the public and the media.  Also, differences in understanding and explaining point in time estimates versus moving averages will need to be considered.  The analyst will also need to know when to report data for a single year, versus a rolling average for three-to-five years of ACS data.

This research will complement Bureau of the Census and US Department of Transportation efforts on analyzing ACS comparison site data.  Possible products of this research study may include guidance manuals for statistical analysis, training courses for MPO and State DOT staffs, detailed case studies of ACS comparison site data, and guidance materials for presenting continuous census data to decision-makers, the public and the media.

COST:  $300,000

DURATION: 24 months

Proposed by the Subcommittee on Census Data for Transportation Planning A1D08(1) and supported by the Committee on Urban Data and Information Systems (A1D08), Committee on Statewide Data (A1D09) and the Committee on National Transportation Data Requirements and Programs (A5016).

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Comments? Send to Ed Christopher (subcommittee chair)