[Talk-GB] Estimating coverage

[Peter Reed]

There have been a number of attempts to estimate the level of UK coverage,
of varying levels of sophistication, but I've not seen any that compare the
length of roads mapped against actual road lengths. 

 

The Department for Transport publishes statistics on actual road lengths by
local authority here
http://www.dft.gov.uk/pgr/statistics/datatablespublications/roadstraffic/roa
dlengths/. 

 

The number of complete administrative boundaries plotted on OSM has shot up
in the last few weeks, so it's now possible to compare actual road lengths
(or at least DfT statistics)  against the lengths of road that are in the
map. 

 

Over the last couple of weeks, I've had a first attempt at doing this for
about 100 local authorities with decent boundaries.

 

Of the authorities I have managed to measure, the following all show more
road mapped than the DfT believes exists:

 


London Borough of Kingston upon Thames

111%


Birmingham City Council

109%


Rutland County Council

108%


London Borough of Richmond upon Thames

107%


Portsmouth City Council

106%


City of London Corporation

105%


London Borough of Waltham Forest

105%


London Borough of Merton

105%


London Borough of Redbridge

104%


Solihull Metropolitan Borough Council

104%


Reading Borough Council

104%


London Borough of Hounslow

103%


Kingston-upon-Hull City Council

103%


London Borough of Sutton

103%


Isle of Wight Council

103%


London Borough of Barnet

102%


London Borough of Islington

102%


London Borough of Enfield

102%


Southend-on-Sea Borough Council

102%


London Borough of Brent

100%


London Borough of Haringey

100%

 

Given the scope for error in all this, the figures don't look too silly, and
at least they suggests a pretty high level of coverage in these places.
Eyeballing the map tends to confirm this. 

 

My measurements on the following authorities show the map holding less than
half the roads that DfT believes exist:

 


Ceredigion County Council

49%


Gateshead Metropolitan Borough Council

48%


Blackburn with Darwen Borough Council

45%


Stoke-on-Trent City Council

45%


Middlesbrough Borough Council

44%


Rochdale Metropolitan Borough Council

42%


Cornwall County Council

42%


Bolton Metropolitan Borough Council

41%


Sunderland City Council

41%


Borough of Telford & Wrekin

41%


South Tyneside Council

40%


Barnsley Metropolitan Borough Council

40%


Darlington Borough Council

34%


North East Lincolnshire Council

33%

 

Again, there is considerable scope for error, but these at least suggest a
low level of coverage in these places.

 

For anyone interested in the technicalities, I am doing this by loading a
Planet OSM extract into a Postgis database. 

 

There are about 100 authorities where I haven't yet managed to extract a
useable boundary, and a number of Counties where the ceremonial boundary
that is plotted doesn't match the administrative boundary used by DfT. 

 

I hope this proves useful - if only so to suggest where to holiday in order
to make the biggest impact. Hint: Cornwall, Cumbria, Norfolk and N.
Yorkshire all seem to have a lot of un-mapped roads.

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