I also made a map of that: http://www.jefftk.com/boston_transit_quality http://www.jefftk.com/boston_transit_quality (details: http://www.jefftk.com/news/2010-1

I also made a map of that: http://www.jefftk.com/boston_transit_quality http://www.jefftk.com/boston_transit_quality (details: http://www.jefftk.com/news/2010-11-17 http://www.jefftk.com/news/2010-11-17) (The map isn't actually 1/time-to-park-street. It's average time from each point to every other point.)