CTPP July 2007

ctpp@listserv.transportation.org

3 participants
4 discussions

by Jonathan Lupton

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

16 years, 6 months

[CTPP] TAZ delineation timeframes

by Murakami

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

16 years, 9 months

Re: [CTPP] 2010 Proposed Criteria - Census Tract/Block Group Changes

by Bob Paddock

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

16 years, 9 months

[CTPP] 2010 Proposed Criteria - Census Tract/Block Group Changes

by John M. Sharp

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/>

16 years, 9 months

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CTPP July 2007