It occurred to me that the "Pay scale areas" that arrived with the OSM Naptan import should be fairly thickly populated areas, so those with a relatively low road density would highlight places where there were roads missing from the map, and hence help to prioritise attention on plugging the gaps.
So for each Naptan area, I calculated road density as the length of roads in km, divided by the area of the pay scale area in sq. km. I've included motorways (and links), primary, secondary, tertiary, unclassiifed and residential roads. I've not included cycleways, paths and bridleways, etc. The database extract I used is a few weeks old (end Dec 2009), but that shouldn't make a lot of difference (unless someone has added a mass of new roads in a particular area). The result can be seen here. http://www.reedhome.org.uk/Documents/osmembedscale.html?kml=KML/naptan.kml <http://www.reedhome.org.uk/Documents/osmembedscale.html?kml=KML/naptan.kml&; title=Naptan> &title=Naptan . The highest quartile of areas (by road density) are shown in blue, then the following quartiles in green, orange and red. In other words red areas have the least road for the area, blue areas have the most, green areas are higher than average, orange lower than average. Looking at the result, the broad pattern is what you would expect, with the south-east of England fairly well covered and gaps further north. But at a detailed level things are not as simple as I had hoped. There is too much variation between the different Naptan areas to make sensible comparisons. Anyway, for what it's worth, this is what it looks like. Maybe someone else will spot a way of making use of the information.
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