I know that this may not be terribly pertinent to those doing single metro areas but at the state and national levels there is this bit of weirdness in the data in which we have multiple central cities in an msa - so a trip from one of these (Rockville Md. ) to another (Arlington or Fredericksburg) is tabbed as a central city to central city trip. For Commuting in America purposes we had to retabulate the files so that there would be comparable data from 80 to 90 - thus ending the central city renaissance of 1990. Now 2000 has a similar attribute. Question: Is there a list of the central cities in each msa/pmsa/cmsa? Wash DC had five last time I think. The message is or ought to be that Some central cities are more central than others!