Hold on, all - aren't we living in a time where "everyone and their little brother" has a GIS?  Nothing either existing now or proposed for the future CTPP is going to prevent anyone from developing zones at whatever level of geographic focus needed.  You can use Census blocks or something even smaller if you want and you're all set to geocode population, housing, local data coded to street addresses and probably detailed employment data (depending on the source you use).  The only thing you won't have at that level of geography is all the info from what the Census used to call the "long form" that you'll just have to allocate down from higher levels of geography like the county.  (Which we all should have been doing all along anyway given the high percentage of either missing or inconsistent answers provided on these longer surveys.)  

Sam Granato
Ohio DOT, Office of Technical Services
1980 W. Broad Street, Columbus, OH  43223
Phone:  614-644-6796, Fax:  614-752-8646
"Platitude: an idea that a) is admitted to be true by everyone, and b) is not true." - H. L. Mencken

From a small (~135,000 pop) MPO perspective, the implications of these
super-TAZs for travel demand modeling are devastating.  If 65K, we would
have two TAZs; if 20K, we would have six or seven.  Fortunately, we are
also an attainment area and are not mandated to do modeling at all;
however a new TMA with population of 200,000 would be so mandated and
would have a total of three or 10, respectively, so it would become
virtually impossible to do modeling for AQ conformity.

The four MPOs (howdy, Larry) along the Front Range are trying to develop
an integrated model for a population of ~3.5 million, so at 65K would
have only 54 TAZs, or at 20K only 175.  The latter number is far less
than we now have (306) in the Pueblo MPO - the smallest of the four.

Bill Moore, MPO Administrator
PACOG MPO/TPR