[CTPP] CTPP Discussion Issues

During the past few months I have received several questions regarding the need for small area, Traffic Analysis Zone (TAZ), data from the American Community Survey (ACS) so I thought I would provide an update. GENERAL UPDATE ON CTPP There are two groups that are working on census data needs for the transportation community. First there is the long-standing CTPP Working Group that meets monthly and has been responsible for the content of the 1980, 1990 and 2000 data packages. Although the precise membership of this working group has changed over time it has generally been made up of US DOT staff, Census Bureau (CB) staff, Dave Clawson from AASHTO, and members of Transportation Research Board (TRB) committees. The work of the CTPP Working Group tends to focus on the highly technical aspects of the data. Since 1997, this group has met at least once a month and has been chaired by Elaine Murakami of FHWA. Working in concert with the CTPP Working Group, the AASHTO Standing Committee on Planning (SCOP) last August (2005) initiated a broader based Committee called the SCOP Census Work Group. Jonette Kreideweis of the Minnesota DOT chairs this group. Its main focus has been on issues that transportation planners need to know to use the ACS and it has been instrumental in recognizing that a “family” of new data products will be needed. In June the Work Group proposed a pooled-fund project that includes data products, research, training, and technical support. The pooled-fund is currently before SCOP and I hope that it will be approved by AASHTO in October. The pooled-fund builds upon the experience gained from the 1990 and 2000 pooled-fund projects and details on it can be found on the TRB Subcommittee on Census Data website at http://trbcensus.com/SCOP/ TAZ DEFINITION for ACS 1. Will MPOs and State DOTs be asked to submit new TAZs? Assuming that a new CTPP pooled-fund is approved by AASHTO, there will be an opportunity to define new TAZs for CTPP data products. Questions to be answered revolve around how many different TAZ systems should there be, the cost for developing those systems and the mechanical process for submitting them. To help define TAZs, discussions with the CB’s Geography Division are underway. 2. How will new TAZs be submitted to the Census Bureau (CB) and added to TIGER? The CB has a contract with M-cubed and its subcontract Caliper Corporation for software development to support the “Participant Statistical Areas Program” (PSAP). The PSAP includes the tract and block group definition process. The software being developed for this program can be modified to accommodate TAZ, SuperTAZ or any other geographic units that the transportation planning community would like to have. As a result, it makes sense to have tract, block group, and the TAZ definition efforts be a coordinated process. Of course the development of any TAZs are premised on and would be paid for by the pooled-fund. 3. When will the Census Bureau (CB) use the new TAZ definitions to tabulate ACS data for CTPP? Since the CB PSAP to define track and block groups is focused on the 2010 regular census, tabulations of ACS data issued in 2010 and after would follow the new geographies. Any earlier products would use existing 2000 geography. For example, the pooled-fund calls for small-area tabulations from ACS data using a required 5-year period -- 2005, ’06, ’07, ’08 and ’09. The data would not be released until 2010-2011 and we have been assured that it would follow 2010 geography. However, for our first 3-year product (2005, ‘06 and ‘07), we have to use 2000 geographic units and meet the 20,000 population threshold per zone. 4. What is the history of TAZ definition for CTPP? For the 1980 and 1990 data tabulations TAZs were restricted to 6 characters and only one set of TAZs could be defined per region. The data assigned to these TAZs represented an equivalency process where MPOs were asked to let the CB know which blocks to assign to which TAZ. Blocks could not be split and the TAZs really became an aggregation of blocks and block groups. In 2000, a major improvement was made where the TAZs were defined early and placed in the CB TIGER file. With the TAZs in TIGER the CB was then able to put the actual data for the area the TAZ represented in the predetermined TAZs. For the first time the “urban” TAZs became a unique tabulation geography and not just an aggregation of Census geographical units. While this new process was adopted for TAZs the equivalency process remained for those areas that crated state-level TAZs. This was due to size limitation of the TIGER record and other technical processing issues. 5. WHAT are some items to consider? As we look toward the future and ACS related transportation data products, further TIGER improvements are on the horizon. Inside the CB the Geography Division is undergoing a major overhaul of its TIGER file data base. Conceptually, TIGER is moving to something akin to a relational data base and space limitations are a thing of the past. Not only can we consider adding more characters to the TAZ field, we can even talk about having different TAZ zone structures. Assuming the AASHTO pooled-fund is approved, one of the first tasks will be to focus on defining TAZs for inclusion into the new TIGER system. As a result, we need to focus on what we want in terms of TAZs. Other items that are nearing the horizon concern the detail data tables to be included in the various products. The pooled-fund is calling for a one, three and five year transportation data product. However, before we work on the specific details of the product design the pooled-fund must first be approved and funded. As Chair of the TRB Urban Data Committee, the sponsoring committee of the Census Data Subcommittee, I hope to see this list serve used as a forum to feed these discussions. Currently we have over 550 subscribers to this list, most who are the active census data users in their MPOs, states, consulting firms and universities. Finally, if you have a question about any of this, please post it to the list serve. We are at a critical time in terms of getting the information out to our various users. So please share your comments, questions and experiences. -- Ed Christopher Resource Center Planning Team Federal Highway Administration 19900 Governors Drive Olympia Fields, Illinois 60461 708-283-3534 (V) 708-574-8131 (cell) 708-283-3501 (F)