­BACKGROUND

The Census Transportation Planning Products (CTPP) data sets and the American Community Survey (ACS) are critical data elements that support analysis of transportation planning, policies, programs, and project selection.  As a result of changes in the data products over the last 10 years, ongoing staff turnover, and emerging technologies, many transportation agencies find themselves without the necessary expertise to use this data effectively to support transportation analyses.  In addition, there is no centralized resource to learn how to use the data for real world applications, resulting in wasted time and resources and questionable analyses.

When the Census Bureau introduced the ACS as the replacement to the Long Form, it brought with it a change in how the data were collected and packaged for public release.  This change in turn brought a whole new set of data issues for the transportation analyst.  Large margins of error, privacy protection rules and procedures, imputation, rounding, data suppression, changes to the survey instrument and variables, and period estimates all have stretched the learning curve for the user.   Staff from state departments of transportation (DOTs), metropolitan planning organizations (MPOs), and transit operators all have struggled with the use and application of the ACS and data products derived from it, such as the CTPP and Public Use Microdata Sample/Public Use Microdata Area (PUMS/PUMA).  A detailed guide addressing these various problems and issues would facilitate improved use of available data and application of related analytical strategies and tools.

OBJECTIVE

The objective of this research is to develop a field guide for the transportation community on how to best use Census data, including the ACS, CTPP, LODES Employment-Household Dynamics (LEHD), and PUMS/PUMA, to address transportation issues. 

The field guide is expected to play a critical role in enabling users at all levels to learn about and apply census data and its derivatives—efficiently, empirically, and economically.  Research teams are encouraged to be creative in their suggestions for alternative media targeted to specific audiences as a final product to increase awareness of the field guide.

STATUS: Research Complete.  Publication under review. To be published as NCHRP Research Report 1108.