Like Ms. Bousefield in Chicago, I find the HUD vacancy figures running
very low. The ACS county-level vacancy data appear far more accurate in
our area, but they are not available at the tract level yet. However,
the HUD data do appear to reflect different characteristics of tracts -
they correctly identify areas of generally higher vacancy. Therefore, I
may be able to use the HUD figures to identify changes in vacancy by
tract over time.
The HUD figures do not separate businesses from residences. Therefore,
like so many other sources, they are useful but not fully compatible
with other data sets.
Jonathan Lupton
Metroplan - Little Rock AR
Recently there have been a number of questions about when to delineate
TAZs for the NEXT CTPP. We are working with the Census Bureau for TAZ
submission for the next CTPP. They have not yet provided us with a cost
estimate for the software. It will be a GIS-based approach, as the
TAZ-UP process was in CTPP2000. We had a meeting on July 25, and the
schedule for TAZ submission into TIGER is most likely going to begin
January/Feb 2009. In the last CTPP Status Report
http://www.fhwa.dot.gov/ctpp/sr0307.htm , we had slightly earlier dates
(I think we said Fall of 2008). By starting a few months later,
preliminary (not final) 2010 Census tract and block group boundaries
will be available as references for TAZ definition.
Many regional models are moving toward smaller and smaller TAZs. In one
case, we heard that TAZs were planned to have an average of 120
households. Because the ACS sample size is so much smaller than the
decennial census "long form" this might result in only 6-10 completed
surveys for housing units, even after 5 years of sampling. We are
concerned that the CB might require TAZ to have the same population
thresholds as "block groups". The CB issued a Fed Reg notice about
raising the population threshold for block groups from 600 to 1200. At
today's meeting, the CB said they had gotten a lot of comments that
people preferred the CB to keep the threshold at 600. TAZs that are
submitted into TIGER for CTPP might need to aggregated your model zones,
for example, two of your model TAZ = 1 Census TAZ, otherwise you might
risk a lot of data suppression based on disclosure avoidance rules by
the Census Bureau's Disclosure Review Board (DRB). We have a meeting
set up for August 23 or 24 with the DRB which we hope will provide more
insight on how they will consider the next CTPP. We are planning to
discuss synthetic data approaches which may result in the ability to
provide small TAZ summaries. The Census Bureau is concerned that
releasing data for very small geographic units results in data with very
large margins of error. They would prefer that larger geographic zones
be tabulated to reduce the margin of error.
Finally, just as a reminder-small area tabulation (like tracts and TAZ)
from ACS is restricted to 5-year accumulation of sample records.
Elaine Murakami
FHWA Office of Planning
206-220-4460
Yes.
Just what the implications are for TAZs in 2010 appear to be
uncertain.
Robert J. Paddock
Transportation Research
Metropolitan Council
390 N. Robert Street
St. Paul, MN 55101
651 602-1340
Is anyone else scratching their heads on the 2010 proposed criteria for
census tracts and block groups?
Making the lowest level for census tracts 1,200 pop and the lowest for block
groups 1,200 pop seems redundant. However, what concerns me are the amount
of potential changes to the fundamental census geographic structure in 2010.
In 1998/99 we sent our TAZ geography to the Census Bureau, so that it could
be included in the development of the 2000 CTPP data. Only a few of our TAZs
didn't match the Census Bureau's criteria for a TAZ (census block group
boundary issues). Does anyone else think that we should wait to do CTPP/TAZ
until "after" the 2010 Census? Due to the overhaul of block groups and
possible changes in geography there is a great chance that we will have to
redo many of our TAZ boundaries. This would be easier if we know the "new"
geography.
Any comments?
Thanks,
John
John Sharp
Program Coordinator
Transportation Planning & Data Services
21 E. Main, Suite 100 Oklahoma City, OK 73104
Telephone: (405) 234-2264 FAX : (405) 234-2200
email: jmsharp(a)acogok.org Website: http://www.acogok.org
<http://www.acogok.org/>
