Elaine,

Please excuse my ignorance.  I have had questions about how the Census Dept. would collect TAZ data for the Census.  I have been waiting for information like you have provided below.  Can you give me any additional information?  We are in the process of modifying our TAZ structure now and want, If possible to use the new information in this count.  Any thoughts?

Thanks,

From: ctpp-news-bounces@chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Elaine.Murakami@dot.gov
Sent: Wednesday, October 06, 2010 10:32 AM
To: ctpp-news@chrispy.net
Subject: [CTPP] TAZ delineation for CTPP (2006-2010) tabulation SCHEDULE

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