I do not think that was DfT - Walker I. Drivers overtaking bicyclists: Objective data on the effects of riding position, helmet use, vehicle type and apparent gender. Accident Analysis & Prevention, 2007 Mar;39(2):417-25.
I have seen that paper and I also seem to remember that someone had done a detailed review of the findings and come to the conclusion that the authors methodolgy did not stack up very well
Different research, I am referring to TRL 549 "Driver's Perception of Cyclists" Author: L. Basford, S Reid, T Lester (TRL Ltd) and J. Thompson 2002
You can download this from the DfT site