Chris: I believe that Caltrans (California Department of Transportation) will be building any new statewide travel analysis zones on MPO-defined zones in our metropolitan areas; and census tracts in non-metropolitan areas. This should be adequate for purposes of developing a statewide TAZ system. <The 4,000 census zones I've defined in my region of 6.8 million people, will probably be collapsed to about 300 statewide TAZes by Caltrans.> On the other hand, it may prove useful to request block group level TAZes in non-metro counties. If I were the county planner in Lake County (the non-metro county just north of my Napa County in Calif.) I would much prefer to get CTPP data at the block group level than tract level (this assumes the absence of TAZes for non-metro counties!) I would hope that the default option for Statewide TAZes are finer-grained than counties!! That doesn't make sense to me. My recommendation would be to monitor the TAZ development in your MPOs; then tally up the number of census tracts and block groups in each of your counties. Depending on the level of detail, and the needs of your local non-metro county planners, decide on either tracts or block groups. Either that, or define TAZes on a block-by-block basis for your entire state. That sounds like a six person month effort to be completed in 30 days from today.... I'm uncertain about the rules established by the Census Bureau, but I believe they're only going to allow one set of TAZes for each county. So, in metropolitan counties, it's apparently up to the MPO and State DOT to negotiate the finest-grained system that meets or exceeds the needs of both <I should be corrected if I'm wrong.> cheers, Chuck Purvis, MTC ******************************************************* e-mail: cpurvis(a)mtc.ca.gov Chuck Purvis, AICP Senior Transportation Planner/Analyst, Planning Section Metropolitan Transportation Commission 101 Eighth Street, Oakland, CA 94607-4700 (510) 464-7731 (voice) (510) 464-7848 (fax) WWW: http://www.mtc.ca.gov/ MTC DataMart: http://www.mtc.ca.gov/datamart/ MTC FTP Site: ftp://ftp.abag.ca.gov/pub/mtc/planning/ Personal WWW: http://home.earthlink.net/~clpurvis/ *******************************************************