At our monthly CTPP Technical meeting last week, April Avnayim of the
Census Bureau Geography Division, gave us an update on the TAZ
delineation software schedule.
November 2010: agencies verify contact names by reviewing file at
Cambridge Systematics ftp site, and report any changes to Liang Long.
December 2010: final delivery of software by Caliper to CB
February 2011: web-based training coordinated with FHWA
January thru March 2011: delivery of software and Census 2010 data and
geographic files on a rolling basis.
Each state will get 3 - 4 months to delineate their TAZ and TADs and
return the files to the Census Bureau.
July 2011: all files MUST be returned to CB Geography Division.
Please note: TAZs for CTPP tabulation do not necessarily match the TAZs
for your travel demand model. Because the ACS sample is small, some
agencies are planning to make the TAZs for CTPP LARGER than their model
TAZs, e.g. combining their model TAZs together. Also, TAZs for CTPP are
census block equivalencies. You will NOT be able to modify the TIGER
segments (which was possible in the CTPP2000). Finally, agencies are
NOT required to define TAZs or TADs. If you do not define TAZs, then
census tracts will be used as the default geography for CTPP (2006-2010)
tabulation. However, even if you do not define TAZs, we recommend that
you create TADs (population threshold of 20,000) by combining census
tracts together.
The TAZ business rules are posted on the FHWA webpage:
http://www.fhwa.dot.gov/ctpp/tazddbrules.htm