Am 11.01.2013 17:24, schrieb Roland Perry:

So we'd have to read the full study (which does seem to be more than
just a handful of trips).

ftp://ftp.hsrc.unc.edu/pub/TRB2011/data/papers/11-0419.pdf

Lots of models and coefficients in few pages, but I can't spot the 30
percent result. "The main dataset is the Rolling Origin and Destination
Survey (RODS), conducted by Transport for London (TfL) or its
predecessor organization London Transport from 1998 to 2005. RODS
records travel paths including the access, transfer, and egress stations
for more than 250,000 trips in the Underground network."
-- Kai Borgolte, Bonn