[Tagging] Merge cycleway=asl/advanced_stop_line/bike_box/...?

Andrew Chadwick (lists) a.t.chadwick+lists at gmail.com
Wed May 23 12:01:34 BST 2012


On 23/05/12 10:52, Gregory Williams wrote:
> There's also http://taginfo.openstreetmap.org/tags/type=advanced_stop_line
> which uses a relation containing the way approaching the ASL and the node of
> the junction of the ASL. With this method it's easier to determine the
> direction of approach to the ASL than just tagging a single node alone.

Thanks for the reminder; we'll have to organise those too. I'm not sure
they're completely consistent:

  http://www.openstreetmap.org/browse/relation/75707
   - 3 ways, all connecting to a central node
  http://www.openstreetmap.org/browse/relation/87140
   - 2 ways, 1 node; ways are in sequence, node is *not* part of one
  http://www.openstreetmap.org/browse/relation/106889
   - two 2-way sequences, 1 node, 1 plain way: 6 members
  http://www.openstreetmap.org/browse/relation/106868
   - 7 ways all in a line, 1 node
  http://www.openstreetmap.org/browse/relation/158262
   - 1 way
  http://www.openstreetmap.org/browse/relation/185408
   - 1 node
  http://www.openstreetmap.org/browse/relation/239790

I assume the model was for 1 node and 1 or more ways connecting to it,
and that the weird ones are degenerate cases. It seems rather subject to
editor rot: though that's the problem with all relations of course.

You cannot determine the location of the ASL itself with your scheme,
which is a bit of an oversight for a geographic database. Additionally
it does not say what sort of traffic the advanced stop line is for. I
think for it to be fully useful it would need to state both.


Still, I'm not averse to relations provided they build on simpler
elements which are easier for newbies to add, and are *only* deployed to
resolve cases of ambiguity. I think there's likely to be very little
ambiguity in practice; my gut feeling is that simple tagging of
locations would be capable of expressing the vast majority of cases
unambiguously. Counterexamples welcome, of course!

At this early stage we get to stipulate that there either MUST[1] or
SHOULD[1] be a highway=stop line "nearby, as part of the same way", and
that both nodes must occur on one, and only one way. Would that be a
workable approach? Do situations like


   -------stop-----[hugegap]-------asl---junc---stop---------

ever occur in practice? I note that even this ambiguity can be resolved
by breaking the way at the junction node.


[1] ... see RFC 2119 ...

-- 
Andrew Chadwick



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