Office of Planning, Environment, & Realty (HEP)
Planning
2006-2008 CTPP based on ACS data has been fully released! Tabulation is limited to areas with 20,000 residential population or more. The data with the access software are available at ctpp.transportation.org. Go check it out! The initial version was released in mid January, and upgrades and bug fixes are rolling in on an as needed basis.
This round of CTPP is using web-based data delivery. Please refer to the article written by Paul Agnello for more information about the data access software.
Census Bureau Geography Division staff.,
geo.taz.list@census.gov
Liang Long, Cambridge Systematics.
Liang.long@dot.gov
February through July of 2011 will be critical months for Traffic Analysis Zone (TAZ) and Traffic Analysis District (TAD) delineation for CTPP. If you are an MPO or State DOT and want the 2006-2010 CTPP to include tabulations for TAZs and TADs, you need to allow enough time to delineate these geographic entities and submit them to the Census Bureau.
For the first time, two different custom geographic zone systems will be allowed. In addition to TAZs, a new geographic area called a Transportation Analysis District (TAD) will be defined. TADs will have a minimum population threshold of 20,000. The concepts behind the TADs are to have a geographic unit that meets the Census Bureau's threshold for 3-year ACS tabulation, 20,000 people per zone and to provide high quality data. Even if a State or MPO chooses not to define TAZs, they should consider defining TADs by aggregating 2010 block groups, 2010 Census tracts, or small rural counties to avoid the "incomplete coverage" problem currently found in ACS standard tabulations (Only cities and counties with more than 20,000 population are covered in ACS standard tabulations).
Note: The figures shown below do not represent the final version of the MTPS TAZ Module; those in the final version may look somewhat different.
The TAZ delineation software is being developed by Caliper Corporation. The software, referred to as the MTPS TAZ Module, has a Geographic Information System (GIS) basis, similar to their Maptitude product and is a stand-alone package that does not require purchase and/or a license(s) to run. The MTPS TAZ Module allows MPOs and State DOTs to delineate TAZ entities (TAZs/TADs) based on 2010 Census tabulation geography (census tracts, block groups, or blocks). The module will have the ability to delineate TAZs only; both TAZs and TADs; or TADs as aggregates of default TAZs (e.g., 2010 Census tracts or block groups). It will also give participants the option of delineating their 2010 TAZs starting from scratch; using their TAZs from Census 2000; creating new TAZs starting from the 2010 Census block groups or 2010 Census tracts; or by importing block equivalency files (i.e., loading your own file in which you have already assigned TAZ codes to 2010 Census blocks). [Figure 1]
Figure 1 - This image shows the TAZ software map display, toolbox, and start (restart) settings available to the participant.
The MTPS TAZ Module will allow the participant to spatially edit geographic data by adding and removing area, as well as creating new and deleting existing TAZ entities. The residential and worker tallies will be updated with each edit that is made to the TAZ entity. [Figure 2].
Figure 2 - The grey area represents the TAZ selected for editing. The population and worker tallies (red circle) change as blocks are added to or removed from the TAZ.
The MTPS TAZ module contains automated checks for nesting and overlap issues. For example, TAZs must nest within counties and TADs; and TADs must nest within the MPO (TADs can cross county boundaries). A variety of participant run checks will help verify that the delineation has adhered to contiguity, compactness, and minimum population/worker count requirements. The module also verifies that there are no unassigned areas and all assigned codes are unique. [Figure 3] Once the MPO or State DOT has completed their work, the module will create a ZIP output file, including new shapefiles and block equivalency files, to return to the Census Bureau's Geography Division.
Figure 3 - One of the verification checks (unassigned areas) that the MPO or State DOT must run to verify the delineation of the TAZ/TADs.
The Census Bureau's Geography Division will have a booth at the TRB Annual Meeting where there will be a demonstration of the preliminary MTPS TAZ Module.
The FHWA, in coordination with the Census Bureau's Geography Division, will host two web-based TAZ software training sessions (webinars), tentatively scheduled for February 25 and February 28, 2011. The webinars will demonstrate how to use the MTPS TAZ module. The webinar will be recorded and archived on the AASHTO CTPP webinar page. http://ctpp.transportation.org/Pages/webinardirectory.aspx
Agencies are not required to delineate TAZs or TADs for the CTPP. If an agency chooses not to delineate TAZs for a county, the 2010 Census tracts will also become the TAZs for that county. Even if agencies do not plan to delineate TAZs, they may want to define TADs by aggregating block groups, census tracts, or counties together.
The TAZ business rules are posted at the FHWA webpage: http://www.fhwa.dot.gov/planning/census_issues/ctpp/data_products/tazddbrules.htm
Penelope Weinberger, AASHTO, Pweinberger@aashto.org
The CTPP Oversight Board met on August 25 and 26, 2010. The meeting was chaired by new Oversight Board Chair Jennifer Finch, Colorado DOT. Jennifer Finch is the Director of the Division of Transportation Management and Planning at the Colorado DOT. During the meeting the draft Mid-Program Report was rolled out. The AASHTO CTPP 2008 to 2012 program is at its midpoint, and highlights of achievements, remaining work and remaining budget are detailed in the Report. The report will be released in late January 2011 and posted on the AASHTO CTPP Website. Highlights include the availability of $1.4 million remaining to commit to CTPP research, training and data needs as seen fit by the Oversight Board. The next Oversight Board meeting is scheduled for February, 2011.
AASHTO has participated in a number of conferences and workshops and more are planned. See the listing below for scheduled training. The CTPP program team is always interested in increasing the data users' capacity to use CTPP products. Please contact Penelope Weinberger to discuss your training needs.
| Training Date | Venue | Training Format | Training Staff |
|---|---|---|---|
| January 23, 2011. 9:00am -12:00 pm, |
TRB Annual Meeting | Conference Workshop | FHWA, AASHTO and Census Bureau |
| February 1, 2011 | Michigan State DOT and MPOs training: | In-person presentations | Ed Christopher |
| February, 2011 | Florida Model Task Force | In-person presentations | Ed Christopher and Liang Long |
| February 25 and February 28 | TAZ Delineation software Training for all MPOs and State DOTs | Webinars | FHWA, AASHTO and Census Bureau |
| March 21, 2011 | Arizona DOT TAZ delineation and data access software training | Hands-on computer software training | Ed Christopher and Liang Long |
| May 8, 2011 | TRB Planning Applications conference | Workshop | Elaine Murakami and Ed Christopher |
Five webinars are archived and accessible on the AASHTO CTPP webpage: http://ctpp.transportation.org/Pages/webinardirectory.aspx. Five eLearning modules are developed or under development and will be made available at: http://ctpp.transportation.org/Pages/elearningmodules.aspx. The five topics covered are:
The first CTPP using ACS with small area tabulation will use ACS records from 2006-2010. AASHTO has been working with the user community to develop a table request. AASHTO is now working with Westat (the contractor for the NCHRP project 08-79, "Producing Transportation Data Products from the American Community Survey that Comply with Disclosure Rules") to generate a final request. The data are expected to be released in 2012. CTPP Website: http://ctpp.transportation.org
AASHTO's CTPP program is jointly sponsoring TRB's Using Census Data for Transportation Applications Conference. AASHTO's partners are FHWA, FTA and RITA. The Conference is scheduled to be held October 27 - 29, 2011 at the Beckman conference center in Irvine, CA.
Calls for papers, posters and sessions will be developed based on the following conference objectives:
We expect the conference to be an excellent resource to the transportation data user community.
Nathan Erbaum, New York State DOT, Office of Policy Planning and Performance, mailto:nerlbaum@dot.state.ny.us
Presently the New York State Department of Transportation (NYSDOT) has three sources available on commutation flow:
Each of these three datasets presents a challenge to the transportation community in terms of which snapshot of commutation flow best meets our needs and is the most representative. The Census 2000 long form and the ACS are sample surveys of housing units and include all workers who went to work. Because of vacations, illness, and other temporary absences, it is estimated that workers "at work" may be about 2% lower than a count of all workers, and about 6% of workers have multiple jobs.1 The LEHD-OTM uses QCEW which uses administrative records of workers covered by unemployment insurance, and does not include self-employed and some other classes of workers, estimated at about 10% of all employment. There is an increasing demand for data at detailed geographic granularity, and survey data with small samples may not be sufficient to meet that need.
The lure of LEHD-OTM is that it provides data for home and work pairs synthesized down to the block level flow and is therefore very attractive for zonal analysis, especially since it is updated regularly. However, as they say, "the devil is in the details." Several issues with LEHD-OTM have already been identified:
Today, the Internet enables us to easily access data through Google searches or web interfaces such as American Fact Finder (AFF) or LEHD on the Map. But the ease of finding data is not matched with finding caveats about the data source. Sadly, it is this author's observation that ease of access to information via the Internet may be causing a problem because people assume that the data are correct and bypass any documentation.
We decided to conduct a review of the 2006 LEHD-OTM and compare it with other sources, including the CTPP2000 and the 2001 NHTS. A number of specific tests were done to look at the flow for each county from the top 5, 10 and 15 originating counties. When comparing the LEHD-OTM to the CTPP 2000 findings included:
When comparing the LEHD-OTM to the 2001 NHTS,
Usual county-to-county flow pairs from the LEHD-OTM which were not observed in the 1990 or 2000 CTPP suggested that the results in New York State had a similar problem with reporting of home and district office for the reporting of employment.
Based on these differences a proposal for further examination of the LEHD-OTM home-to-work flows in other states besides New York was submitted to the NCHRP 08-36 program. This proposal was selected for funding, and Task 98 is currently underway by Cambridge Systematics.
In late August 2010, the CTPP 3-year file which uses 2006-2008 ACS became available. NYSDOT decided to examine how the 3 year data compared with the flow data it had posted on its website for the 1990 and 2000 CTPP https://www.dot.ny.gov/divisions/policy-and-strategy/darb/dai-unit/ttss, under the heading Journey to Work Interactive Application. This webpage was developed to assist our regional staff in easily accessing the Journey to Work data.
We decided to compare the three sources of county-to-county worker flows. Comparing Census 2000 with the CTPP 2006-2008 estimate of flow requires the use of the Margin of Error (MOE), because the ACS sample is so small compared to CTPP2000. In reality the MOE for the CTPP2000 flow data should also be used. Perhaps the LEHD-OTM should also include an MOE measure, since it is a synthetic universe based on QCEW, combined with administrative records, with model-based assignments of matches between workers and business establishment addresses. But unfortunately this is not available either. It would be best if we were able to provide a convergent validation between the sources that would give a snapshot of the data so the elements that don't match could be culled out and further analyzed. The CTPP 2006-2008 is limited to counties with over 20,000 population, compared to CTPP2000 which covers all counties. Figure 4 shows some results of the comparison across three data sources for Queen County, NY.
Figure 4 - Sample results of Journey To Work Flow Comparison - Queen County, NY .
Why is such a 3 way comparison necessary? When methods are complex, different and sources as well as definitions vary, how these factors impact the results is more important to people than their methods of construction. If a data point looks right (as in agreeing with CTPP 2000), or if the differences are perceptibly low, then one can conclude that the data are correct. However, if the opposite is true, than this must also be checked.
While NYSDOT was in the process of analyzing these three data sources, we learned that one of our Metropolitan Planning Organizations (MPO) was in the process of updating their regional transportation model. Their consultant was using the LEHD-OTM data and was experiencing some issues with trip generation and assignment to the network. The mere fact that they were encountering problems in the block level detail that LEHD-OTM could provide suggested that at a minimum, some comparison should be undertaken to illustrate where the flows seemed to be comparable and where there were significant discrepancies. The comparison process enables us to shine a light on where things work, and also where they don't work, and enables people to ask questions about the reasons the numbers are different. We must rely on available data. Therefore, having a full understanding of how well it works can shine a light on any problems that may need to be fixed. NYSDOT's web link to this comparison analysis is located here: https://www.dot.ny.gov/divisions/policy-and-strategy/darb/dai-unit/ttss/cttp_acs/?nd=nysdot. Most of the relevant caveats are listed towards the bottom of the page.
We found that although the counts may vary, when the O&D analysis was done as proportional shares, the data looked more comparable. Therefore, one of our recommendations is that using proportional shares to compare across these data sets may be more useful than comparing counts of workers. We should keep in mind that people often inquire about size, share and change for many measures. We are often asked for comparative data, for example, what is the commutation flow between Queens and Manhattan, how does it compare with the other counties within NYC, and how has the value changed over time. The issue of assuring that the data are reliable, representative and can be used must be demonstrated. Equally important is that the end users need to understand the impact of small samples on their decisions.
Ed Christopher, FHWA Resource Center Planning Team, mailto:edc@berwyned.com
| Data Product | Planned Release Date |
|---|---|
| 3-year CTPP (2006-2008 data) | January 2011 |
| 3-year ACS (2007-2009 data) | January 2011 |
| 2010 TIGER Files (new Block, Block Group and Tracts) | Flow Basis completed by end of February 2011 |
| 2010 Census Population Counts for all Census geography (PL 94-171) | By April 1, 2011 |
| TAZ/TAD Delineation Software Deployed | March through April 2011 |
| TAZ/TAD Delineation Completed | June to early July 2011 |
| 2010 Census Summary File 1 | June to August 2011 |
| New PUMAs Defined | Fall 2011 |
| ACS(2010), ACS (2008-2010) and ACS (2006-2010) | Fall 2011 |
| New Urban Areas Released | Spring 2012 |
| 5-year CTPP (2006-2010) |
Fall 2012 |
| TIGER with Urbanized Areas and Urban Clusters | Fall 2012 |
NHTS Version 2.0 ReleasedThe Federal Highway Administration announced the enhanced 2009 NHTS data (Version 2.0) in November 2010. The enhanced NHTS data features improved methods of processing outliers and population controls using the 2008 American Community Survey. The Version 2.0 data file is now available for download on the Online Analysis Tools page at http://nhts.ornl.gov/. The Online Codebook Browser has been updated and the User's Guide is available at the Publications page at http://nhts.ornl.gov/. |
Bruce Spear, Cambridge Systematics, Inc.,bspear@camsys.com
High quality employment data including workplace location, industry type, and number and geographic distribution of workers, are critical to transportation planning and policy analysis. For several decades, transportation planners have relied heavily on journey-to-work data collected as part of the decennial Census long form to obtain workplace location and distributions of home-to-work trips. However, the replacement of the 2010 decennial Census long form questions by the continuous sample American Community Survey (ACS) has raised concerns within the transportation planning community about the adequacy of the sample size to provide reliable data on workplace locations and home-to-work flows. Consequently, alternative data sources are being examined.
Two public sources of employment data are the Bureau of Labor Statistics' (BLS) Quarterly Census of Employment and Wages (QCEW), and the Census Bureau's Longitudinal Employer Household Dynamics "On The Map" (LEHD-OTM) data. Although neither of these databases were developed specifically for transportation planning purposes, they each hold significant promise. However, many potential users in the transportation community are unfamiliar with these data sources, and lack key information on how the data was collected, limitations and caveats on use, or even where to obtain the data.
The purpose of this research study is to develop a guidebook that provides key information for transportation planners on the QCEW and LEHD-OTM data with respect to how they are collected, how to access and use the data, and their uses and limitations for transportation planning applications. Additionally, the guidebook will identify opportunities for improving the underlying data.
The research study is approximately halfway completed, with a scheduled completion date of July 2011. Work to date has focused on 1) a comparative review of publicly available QCEW and LEHD-OTM data products; 2) preparing for interviews of selected state employment security agencies regarding current agreements and issues in sharing more detailed employment data with other state and local agencies, particularly state DOTs and MPOs; 3) creating a nationwide county-to-county database of home-to-work flows from the LEHD-OTM.
1 Chuck Purvis in CTPP Status Report (May 2003) http://www.fhwa.dot.gov/planning/census_issues/ctpp/status_report/sr0503.cfm (accessed 12/23/2010)
CTPP Hotline - 202/366-5000
Email: ctpp@dot.gov
CTPP Listserv:http://www.chrispy.net/mailman/listinfo/ctpp-news
CTPP Website: http://www.dot.gov/planning/census_issues/ctpp
FHWA Website for Census issues: http://www.fhwa.dot.gov/planning/census_issues/
2005-2007 ACS Profiles: http://download.ctpp.transportation.org/profiles_2005-2007/ctpp_profiles.html
AASHTO Website for CTPP: http://ctpp.transportation.org
1990 and 2000 CTPP downloadable via Transtats: http://transtats.bts.gov/
TRB Subcommittee on census data: http://www.trbcensus.com
AASHTO Jennifer Finch, Jonette Kreideweis, MN DOT Census Bureau: Housing and Household Economic Statistics Division Brian McKenzie FTA |
FHWA Ed Christopher Liang Long TRB Committees Clara Reschovsky Kristen Rohanna |
CTPP ListservThe CTPP Listserv serves as a web-forum for posting questions, and sharing information on Census and ACS. Currently, over 700 users are subscribed to the listserv. To subscribe, please register by completing a form posted at: http://www.chrispy.net/mailman/listinfo/ctpp-news On the form, you can indicate if you want e-mails to be batched in a daily digest. The web site also includes an archive of past e-mails posted to the listserv. |