[Tagging] Proper way to tag highways located in "dangerous" areas

Rory McCann rory at technomancy.org
Wed Nov 16 10:36:07 UTC 2016

I don't think tagging access=destination is a good idea. The access tag
is used for the legal restrictions for a road. access=destination means
you can only legally go on the road if your destination is on it. A
router won't route you down a road that it thinks you (legally) can't go
down. Tagging that way will stop the router routing you on it, but for
the wrong reason. You're "tagging for the router".

Many countries use access=destination to mean this, I suppose the
Brazilian community could use the tag in a different way, but it'd
usually better for us all to use the same tag/values. 🙂

There are some possible solutions to your problem:

Are slums/flavelas (sp?) tagged/mapped in OSM? If so, a router may be
able to downgrade roads that are near a slum by looking at what's nearby.

Do the roads in slums have any common physical properties? Like always
being narrow, with no footpaths, lower speed limits, etc? You could map
those attributes, and a router might be able take them into account. (A
narrow road with pedestrians walking on it, and a low speed limit might
be downgraded compared to a more straighter, easier-to-drive road).

The idea of using an external dataset to inform routing isn't new. Some
bicycle routers use external elevation data to not route people up and
then down a hill. Perhaps there's a dataset of crime/damgerous areas you
could combine with OSM data to make a better router.

However I don't know if any/many routers currently support this kind of
features. So people might just want to keep using the routers they have
and "fix" them.

On 16/11/16 02:04, Nelson A. de Oliveira wrote:
> It's the second time that we are having a major discussion here in
> Brazil, on how to tag highways located in "dangerous" areas.
> For example, some people consider slums and other communities as
> dangerous (since there is a risk of being robbed or even killed) and
> would like to don't have the router creating a route through them,
> using "access=destination" in every street located in such places for
> this, for example.
> Since they can't find another tag to indicate those "dangerous"
> places, they argue that access=destination is valid for this case.
> Other group (including me) find that this is wrong: we should not tag
> streets considered dangerous in OSM (specially when "dangerous" is
> subjective).
> We also think that access=destination is being wrongly used for this.
> Since we can't reach a consensus on this, we would like to hear some
> opinions and suggestions on how to handle such problem, please.
> I had one idea where such data should be kept outside OSM, and
> inserted in some post-processing phase (for example, tag every highway
> that is inside these areas with any needed/wanted property).
> Comments, please?
> _______________________________________________
> Tagging mailing list
> Tagging at openstreetmap.org
> https://lists.openstreetmap.org/listinfo/tagging

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