[OSM-talk] Misclassified roads

Steve Hill steve at nexusuk.org
Thu Jul 10 10:20:27 BST 2008

On Thu, 10 Jul 2008, elvin ibbotson wrote:

> 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?

I know that they are not unclassified, but couldn't tell you what they 
really are without actually going and surveying them.  So my plan was to 
retag them as highway=road so that it would then be easy to see which ones 
still need to be resurveyed to fix the classification.  But whilst doing 
this I realised just how many such roads there are and wondered if it 
would be better to just retag them all to highway=road and then resurvey 

> How on earth did you arrive at this figure? Wouldn't 'guess wildly' be a
> better verb than 'estimate'?

No, it isn't a wild guess, it is an estimate based on looking at which 
roads are tagged as highway=unclassified and using my knowledge of which 
ones definately aren't unclassified roads.

> 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.

So how would you go about making highway=unclassified a meaningful tag, 
given how many roads on the map are tagged as highway=unclassified even 
though they definately aren't unclassified roads?

> What are peoples' views on this? 

Thats what I hoped to find out by starting this discussion. :)

I expect a lot of "no, we don't want any bulk changes" responses, but I'm 
interested if anyone has a better idea.

> The grey area for me is in
> the tertiary/unclassified/service/residential area.

Yes, this is certainly a grey area.  For me, I interpret them as:

   A minor road, usually with a dotted line along the middle.

   Narrower than a tertiary, usually without a dotted line along the middle 
and usually with a relatively high speed limit (although you might not 
want to drive anywhere near that speed :)

   Roads in housing estates - they probably look like tertiary roads, but 
have houses along them (I actually don't like this classification and 
think they would be better tagged as highway=tertiary and 

   Something similar to an unclassified road, but used for access rather 
than a through road.  Usually with a low speed limit.

However, despite the grey areas, I'm not really discussing the 
classifications themselves, I'm trying to work out the best way to "fix" 
the problem that for a long time highway=unclassified has been used by a 
lot of people as a "catch all" for "a road, I don't know the 
classification" (maybe because they were traced from Yahoo rather than 
surveyed, or the submitter couldn't remember what the road was like when 
tracing the GPS track).

> 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.

From Map Features:

Tertiary: Generally for use on roads wider than 4 metres width, and for 
faster/wider minor roads that aren't A or B roads. In the UK, they tend to 
have dashed lines down the middle, whereas unclassified roads don't.

So the difference between highway=tertiary and highway=unclassified is 
defined - you don't need road signs for this.

  - Steve
    xmpp:steve at nexusuk.org   sip:steve at nexusuk.org   http://www.nexusuk.org/

      Servatis a periculum, servatis a maleficum - Whisper, Evanescence

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