From: Steve Hill <[EMAIL PROTECTED]>
Date: 9 July 2008 15:36:03 BDT
To: talk@openstreetmap.org
Subject: [OSM-talk] Misclassified roads
Following the approval of the highway=road tag, I've set about
aggressively changing a lot of the highway=unclassified roads
around Swansea, that I believe are misclassified, to highway=road,
with the intention that they can then be surveyed and reclassified
correctly.
If you believe they are wrongly tagged (I would avoid the word
"misclassified" when referring to an unclassified road ;-) presumably
you have a good idea what classification they are, so why not just re-
tag them as primary, tertiary or whatever?
However, after starting to do this, I've realised just how many of
the roads are misclassified - I'd estimate that well over 80% of
the roads tagged as highway=unclassified are, infact, not
unclassified roads.
How on earth did you arrive at this figure? Wouldn't 'guess wildly'
be a better verb than 'estimate'?
So I'm wondering about the merits of changing *all* the
highway=unclassified roads in the area to highway=road so that the
whole lot can be classified appropriately from scratch.
No way! I personally have mapped hundreds of roads, a high proportion
of them unclassified (and I suspect I am not the only one who knows
what this means) and would not want anyone 'aggressively changing' them.
This would make it obvious which roads really are unclassified and
which need to be checked.
What are peoples' views on this? I imagine that much of the OSM
world is affected in the same way, and this renders the
highway=unclassified tag relatively meaningless in it's current
state. Should there be a global reclassification to fix this, or
is there a better way?
There's always a better way. I suspect the motorway/trunk/primary/
secondary/tertiary/unclassified hierarchy was derived from Britain's
highway classification system, since it appears to be a perfect match
and OSM's roots are here. I don't have much knowledge of how roads
are classified elsewhere, but I guess most countries have
classification systems which can be made to correspond to this
hierarchy. The grey area for me is in the tertiary/unclassified/
service/residential area. C-class roads in the UK are not labelled as
such on road signs or maps (and of course we shouldn't look at maps
as this might infringe copyright ;-) so if you don't work for the
local highway authority you can only guess at what's tertiary and
what's unclassified. In rural areas I tend to tag roads wide enough
for cars to pass as tertiary and narrow lanes as unclassified. How
many houses are needed for the residential tag is obviously a matter
of judgement as is application of the service tag. I have seen some
wrongly tagged roads but I would guess nearer 5% than 80%.
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