[OSM-talk] Divided roads proposal
Steve Bennett
stevagewp at gmail.com
Sun Dec 6 21:16:37 GMT 2009
On Mon, Dec 7, 2009 at 2:31 AM, Lester Caine <lester at lsces.co.uk> wrote:
> grow from nothing to several meters. At what point do you change from
> 'divided'
> to separate ways, which then begs the question
This is the same kind of question as when a road switches from tertiary to
secondary etc. Does it need a firm answer? It would only be problematic,
IMHO, if a road was frequently switching from one form to the other.
> - why have divided if it's just a
> shorthand for two ways with opposite directions.
>
I don't think it is "just a shorthand". In many cases I would put it the
other way: "two ways with opposite directions" is "just a kludge" for a
single divided road. Up until now, we haven't had a way to properly tag a
single divided road, so we do it with two ways. We can fix that.
> You need to justify the real need for it. I'll continue to map the actual
> structure, and add the additional ways for the related footpaths. I don't
> see
> the need for this shorthand for many of the cases you are trying to make?
>
If you're mapping every footpath, you are clearly working at a different
level of detail. It's great that your area apparently has every road already
covered already. Mine doesn't.
To put it differently, the "real need" is to be able to efficiciently map
areas which have divided roads, without resorting to micromapping them as
two ways. I understand that you wouldn't use this tag. But would you object
to others using it?
>
> I think what YOU are missing is that in most cases where there are traffic
> islands which add one way sections of way, they ARE mapped. Around here
> there
>
Yes. And does mapping a traffic island as a splitting of a road into two
ways not scream "wrong!" at you?
Example:
http://www.openstreetmap.org/?lat=-37.820693&lon=144.919989&zoom=18&layers=B000FTF
This looks right to you?
> was an attempted to remove some of them, but that has been rolled back, so
> where
> a road splits, the correct direction ways are added. Routing does not then
> need
> to run through lots of additional tags to find if it can then do a maneuver
> ...
>
One key for ways, one key for junctions. Trivial stuff.
>
> I think it is essential that slipways are mapped. ESPECIALLY when one is
> trying
> to add the right routing instructions. TomTom has started showing motorway
> and
> major road slipway details properly. You need to know when to get to an
> inside
> lane and take a slip road PRIOR to the actual junction.
Maybe we should be mapping slipways, hopefully there's a better approach
than marking them all as fully fledged roads though.
> These are no different
> to the island details approaching a roundabout, so trying to 'save time' by
> not
> actually adding quite important detail does seem wrong?
Even if it were the case that this was "important detail" which I was
proposing not adding, it wouldn't be "wrong", because surely a slipway here
is not as important as a whole road not mapped somewhere else.
>
> Example 3 is no more than a wide 'double line' road marking. SO is it a
> 'divided' or is it simply a road marking?
Either way, we currently have no way of marking it.
> The problem with the proposal is that
> it does not have any indication on when it should be used ...
Other than, say,
http://wiki.openstreetmap.org/wiki/Proposed_features/Divided_road#Scope
Steve
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