Paul: The simple answer is no. No data from the ACS is currently available at the block group or block level. You will need to use Census 2000 (SF1, PL 94-171) to get any kind of data at the block level. For the block group level, you can use almost any Census 2000 product (SF1, PL 94-171, SF3, CTPP-Part 1). The ACS will never, ever produce or publish data at the block level. The ACS is a sample survey, and the Census Bureau will never release sample data at the block level of geography. Block *group* data could or should be published by the Census Bureau based on five-years of ACS data (2005-2009) as early as Fall 2010(?). Then, the Census 2010 data will start kicking in with the PL94-171 data released by the spring of 2011. For aggregate travel model validation, on the other hand, the mid-decade ACS data can be very, very useful. Right now, you can get validation tables such as households by household size; households by number of workers in the household; and households by number of vehicles available in the household. I think these are quite useful for your "demographic model" validation. Also, the journey-to-work data is being published, so that you can produce "observed home-based work trip ends by means of transportation" by area-of-residence as well as area-of-work. Depending on the size of your region, you may be stuck with county (as long as the county's total population is > 65,000); or you may be able to use the data published at the Public Use Microdata Area (PUMA) level. These are the Census 2000 PUMAs, and are "standard census geographic areas" that were defined by the state data center network, and are all 100,000+ in total population. If you're working with smaller counties (20,000-65,000 population) then you'll have to wait for the 3-year ACS data products, based on the 2005-2007 period, which will be released as early as Fall 2008. cheers, Chuck Purvis ************************************************************** Charles L. Purvis, AICP Principal Transportation Planner/Analyst Metropolitan Transportation Commission 101 Eighth Street Oakland, CA 94607-4700 (510) 817-5755 (office) (510) 817-7848 (fax) cpurvis(a)mtc.ca.gov (e-mail) www: http://www.mtc.ca.gov/ ************************************************************** Hi all, We are about to undertake a model validation. As part of the validation, the socio-economic inputs (housing, population, etc.) will be updated. We've searched the Census website for data, but so far we've only been able to find ACS data at the county level. Is there any ACS data available at the block group or block level? Paul H Flavien PBS&J Planner- Transportation Planning 1901 Commonwealth Lane Tallahassee, FL 32301 (850) 575-1800 ext: 7884 Fax: (850) 575-1083 phflavien(a)pbsj.com