http://www.nctr.usf.edu/2012/12/journal-of-public-transportation-vol-15-no-… I am always on the lookout for people using CTPP data. Although this project used CTPP 2000, I thought it was interesting. They analyzed MSAs with population over 500,000. They categorized the MSAs into 3 groups by population size (500,000 to 1,000,000 ; 1 - 5 million; and all MSAs). They found "no relationship between the strength of the CBD (employment) and transit ridership" and found that service frequency was the most strongly related to transit commute mode share. Since the 2006-2010 CTPP should be out in the next several months, this analysis could be re-done with more recent data! To define CBDs, they started with census tracts defined in the 1982 Census of Retail Trade and then modified based on local consultation. Elaine Murakami FHWA Office of Planning 206-220-4460 (in Seattle)