OpenStreetMap
I now have a list of the top z=12 tiles in the UK for where there are "orphaned" bus-stops, i.e. likely to be lots of missing roads in these areas.
The list is here: http://splintmap.geog.ucl.ac.uk/~ollie/lonelybuses/stats.php
More info about this on my blog:
http://oliverobrien.co.uk/2010/03/on-lonely-buses-and-orphaned-bus-stops/
http://oliverobrien.co.uk/2010/03/uk-mapping-priority-areas-by-bus-stop/
Discussion
Comment from robert on 23 March 2010 at 18:23
Dude, you rock.
Though I think your metrics have gone a bit wrong with the London results. The sheer number of bus stops is pushing the number of false positives over the limit.
Comment from Wynndale on 23 March 2010 at 20:32
Most of the red stops in London appear to be either misplaced or on misplaced roads, which is a different issue but still worth tackling.
Comment from Mappo on 25 March 2010 at 15:23
Does the Naptan info not also have street names (and larger localities)? It would be similarly interesting to see which of those names are not currently in OSM. I suppose the data might need some massaging but if the data exists it shouldn't be impossible.