A. The CTPP 2012-2016 data are available through our full data website https://ctpp.transportation.org/ctpp-data-set-information/
A. No. You can access the CTPP 2012-2016 data without registration, but to save your own geography selections or upload custom geographies for selections or retrieve past work you MUST register. The registration is free to all users.
A. Key differences are:
A. The key differences are:
| CTPP 2012-2016 data | CTPP 2006-2010 data |
|---|---|
| It is based on 5 years of ACS data collected between 2012-2016. | It is based on 5 years of ACS data collected between 2006-2010. |
| It is one third the size of the 2006-2010 CTPP data due to Census Bureau restrictions. Only limited tables are available down to small geographies; most tables are available at place, county and other large geographies only. | All tables are available for small geographies including Census Tracts and TAZs. |
| Some worker records are missing for smaller geographies because of incomplete workplace address reported by respondents, which means the sum of the worker counts for these smaller geographies will differ from the single estimate for larger geographies such as county. See more details on place of work allocation. | Worker counts for small geographies are consistent with large geographies, i.e., small geography data when aggregated to large geographies are the same or similar to large geography data. A place of work (POW) extended allocation system was developed and implemented by the Census Bureau to improve workplace allocation data. |
| There are four new tables added: Poverty Status by Means of Transportation at both residence and workplace, Mean Number of Persons per Household at residence, and Vehicle available in household by number of workers in household flow table. | Means of Transportation crossed with Age of Worker, Time leaving/arriving, travel time, income, vehicles available, Minority Status, number of workers in households, and Presence of Children available. |
A. TAZs in CTPP are called Census TAZs and they were delineated by MPOs and State DOTs for the CTPP tabulation purpose. Some regional models now use very small TAZs which would have no ACS samples for tabulation, therefore larger census TAZs were delineated. TAZs will be discontinued in future tabulations.
A. TAD is a large geography based on census TAZs, it has been included in CTPP product since the CTPP 2006-2010. TAD has a population threshold of 20,000. TADs will be discontinued in future tabulations.
A. TAZs in CTPP are called Census TAZs and they were delineated by MPOs and State DOTs for the CTPP tabulation purpose. Some regional models now use very small TAZ which would have no ACS samples for tabulation, therefore larger census TAZ were delineated.
A. Like the 2006-2010 CTPP data product, the CTPP 2012-2016 is a mix of modeled and actual data. Set A tables are based on non-disclosure proofed microdata (actual data) and Set B tables are based on disclosure proofed microdata (modeled data). Row and column totals do not match for the same population and geographies between Set A and Set B, but differences should be within 10%. Please refer to NCHRP 08-79: Producing Transportation Data Products from the ACS that Comply With Disclosure Rules report for details on disclosure proofing process utilized in the CTPP 2006-2010 and 2012-2016.
A. The rounding rules apply to both Set A and Set B tables. For example, values are rounded to the nearest 5 (e.g. 263 is rounded to 265). The cell suppression rule (there must be 0 or at least 3 or more samples to show the table) and the table suppression rule (if any one cell in a table is suppressed, the whole table is suppressed) only apply to Set A non-disclosure proofed data. Please refer to the CTPP E-learning module - Disclosure Proofing ACS Data in CTPP for details on the Census Bureau disclosure rules.
A. The simple answer is that the data are different. CTPP uses ACS data, while Longitudinal Employment Household Dynamics (LEHD) Origin-Destination Employment Statistics (LODES) uses administrative records. The ACS is a collection of responses from a sample of residential addresses. CTPP is a custom tabulation of the ACS, which presents additional confidentiality issues as the number of cross tabulations increases. The LODES uses the Quarterly Census of Employment and Wages (QCEW), which is a list of employers and their employees for whom unemployment insurance coverage is provided. The QCEW may have a business address that is not the same as a workplace location. An estimated 10 percent of workers are self-employed and are not included in the QCEW. FHWA has compared the employment data among CTPP, LODES and the Current Population Survey (CPS), and the article can be accessed from the October 2013 CTPP Status Report.
A. The 2012-2016 CTPP data is based on the 2012-2016 American Community Survey products, which are the estimates of the entire population. All estimates produced from sample survey have sampling errors associated, the 2012-2016 CTPP product provides the Margin of Error for its estimates as measurements of the sampling error. To find out more about the quality of the data from the ACS Data Handbook.
A. If there is another data source that can provide reliable data for the geographic area, you may want to consider using that other source. However, if it is important to compare the results of different geographic areas to each other, one might still be better off using the ACS derived dataset since the survey methods have been applied consistently across all areas of the United States. Be sure to test the significance of any comparisons to ensure that they are statistically acceptable for your particular needs. It may also be important to make sure that the margin of error (MOE) is not larger than the midpoint or value of the original data. For example, if the number of people who walk to work is 326 and the MOE is 350 you should not use the data. For additional help, please visit the U.S. Census Bureau's ACS webpage.
A. There are several calculators and guides.
A. The sample sizes for the 2000 decennial Census Long Forms were much larger than the ACS, even after 5 years of accumulating ACS responses. The associated MOEs for CTPP 2012-2016 and 2006-2010 estimates are therefore larger in geographical areas containing relatively small sample sizes. To calculate the MOE for the Census 2000 long form results, please go to the ACS Statistical Analyzer project, created by The National Center for Transit Research (South Florida) http://www.nctr.usf.edu/abstracts/abs77802.htm.
A. The full dataset is available in flat format, it is available with supporting metadata and documents via: http://ctpp.beyond2020.com/ctpp1216/.
A. The 2006-2010 CTPP data is available for download through the CTPP data website, the full datasets are available at: http://ctpp.beyond2020.com/. The 1990 CTPP data product is available at the Bureau of Transportation Statistics CTPP webpage.
