I am aware of three ways to construct nationwide tables from Census 2000.  As Wendell points out, first, please be sure of which geography you want: MSA/CMSA (Metropolitan Areas), Place (Closest to city definitions), Urbanized areas, urban clusters etc.  For any of these areas, there are different, but easy methods to aggregate the data for the nation. 

Then, please be aware that public transportation may sometimes include Taxicabs, and sometimes they may not.  It is often best to add up the disaggregate modes that are available in the manner you see fit for your analysis (18 total categories in Census 2000)

1. If you have access to SAS software, you can obtain some of these files from the Missouri State Data Center (SDC) at http://mcdc2.missouri.edu/cgi-bin/uexplore?/pub/data/sf32000

2. American Factfinder is very useful in summarizing “geography within geography”, but the geographies are limited to 7,000 from their website (so this should work for state, county, MSA, Urbanized area geographies).  AFF outputs are easy to understand and take the least effort.

3. For place and tracts (which may number more than 7,000 geographies), the easiest I’ve found is to use the BTS Transtats website: http://www.transtats.bts.gov/Tables.asp?DB_ID=630&DB_Name=Census%20Transportation%20Planning%20Package%20%28CTPP%29%202000&DB_Short_Name=CTPP%202000

Place codes for Census 2000 may be found using the special product STP64 on the CTPP website.  Please see attached.

http://www.fhwa.dot.gov/ctpp/stp/stp64.zip

Thank you

Nanda Srinivasan