Last October Elaine Murakami posted an email to this listserve
(http://www.chrispy.net/pipermail/ctpp-news/2006-October/001517.html)
updating folks on the discussions that are underway between FHWA and the
Census Bureau (CB) Geography Division regarding the definition of new
TAZs to be used for the 5-year special tabulation of the ACS data.
Since that time further progress has been made. It looks like MPOs and
State DOTs would be working on their TAZs toward the end of 2008 and
early 2009 with TAZs being submitted in the middle of 2009. This is
important because many areas are already preparing their work programs
to cover this time frame. Exactly, how much work will be involved is
not yet known.
The plan (desire) is to use a GIS-based approach similar to that used
for the TAZ definition for the CTPP2000. We would like a system that
does not require special licensing of GIS software and is user friendly
much like the TAZ-UP effort used for CTPP2000. As an historic note, the
TAZ-UP program for CTPP2000 was developed as an add-on to ArcView 3.1
and required users to have a licensed version of ArcView.
Currently, FHWA staff has asked the CB to plan for the software to
create three levels of TAZs that nest within each other. The smallest
is a base TAZ that would be similar to the traditional small area
geography TAZs used in 2000 and 1990 . The next size, or medium sized
TAZs, would be aggregates of the base TAZs (about 4,000 population) and
the larger size (about 20,000 population) TAZs would be aggregates of
the medium TAZs. This is very akin to Blocks being aggregated to Block
Groups and then Block Groups being aggregated to Tracts. All of these
geographies could be aggregated to PUMAs if desired by the MPO/State.
And of course, all zones would have to nest within counties.
There are still quite a few details to be fleshed out but for now it is
important to recognize that some staff time on the part of the MPOs and
States will be required if an area wishes to define TAZs. Updates to
these activities will be posted on this listserve and in quarterly
Status Report newsletter which can be found online at
http://www.trbcensus.com/ or http://www.dot.gov/ctpp
--
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)
