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Subcommittee on Census Data For Transportation Planning
Subject: Agencies that want to define new TAZs or alter
              TIGER/Line 2000 TAZs
   Date:  Thu, 21 Jun 2001 12:09:00 -0400
   From: "Nanda Srinivasan" <Nanda.Srinivasan@fhwa.dot.gov>
       To:   <ctpp-news@chrispy.net>

Several agencies have written to the CTPP Working Group asking: If TAZs defined in TIGER/Line 2000 can be altered/changed.  Can an agency submit new TAZs in Urban areas based on TIGER/Line 2000 geography for CTPP 2000?

The CTPP Working Group met on June 14, 2001 to discuss these issues.  We
decided that agencies could define new TAZs or alter TAZs in TIGER/Line 2000 and obtain CTPP 2000 data reported for the new TAZs.  However,
agencies must use Census 2000 tabulation blocks to build new TAZs or alter
existing TAZs.  In effect, an equivalency file between census blocks and TAZs will be built and used, as was done in previous censuses.

However, due to processing issues and schedule considerations, agencies
wishing to do this should note the following: 

1. Cost:  To change TAZs or define new TAZs, agencies must separately
contract with the Census Bureau, Journey to Work Branch, and work out a
process and cost for defining and obtaining CTPP 2000 data based on the new TAZs.  

2. Schedule: CTPP data will be processed for those agencies after the
Standard CTPP 2000 products are released for the whole country.  Currently,
the expected completion date for CTPP 2000 is June 2003. 

3. Exclusion of the changes from TIGER/Line database: There are no plans or processes in place to include new TAZs in the TIGER/Line database.  Thus, the changes will not be reflected in TIGER/Line 2000 and it is unlikely
that new TAZs will be inserted into TIGER until the next round of TAZ
updating, the date of which has not been scheduled. 

For more information, please contact Phillip Salopek, Census Bureau,
Population Division (Journey to Work Branch) at 301-457-2454 (e-mail:
phillip.a.salopek@census.gov).

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