[OSM-talk] OpenStreetMap routing service
benlaenen at gmail.com
Mon Sep 8 16:37:24 BST 2008
On Monday 08 September 2008, Nic Roets wrote:
> On Mon, Sep 8, 2008 at 3:23 PM, Lars Aronsson <lars at aronsson.se>
> > Here you assume that "trunk" is a well defined concept. But it
> > isn't.
> Spot on.
> And defining things per country leads to all sorts of problem. For
> example mappers applying domestic rules when visiting foreign
> countries. Confusion when debugging routing software. Next mappers
> will omit units of measurement because they feel it it's implied for
> their country.
> The solution is for editors to create defaults for these disputed
> access restriction tags and allow users to change them before
> committing them to the database.
I strongly disagree. There are so many country specific rules that it'd
be naive to think you can twist everything into one system that applies
If you're in a country where trunk means a road where no pedestrians or
cyclists are allowed, then adding that information in the database is
unnecessary. This makes sure that
(a) if for some reason the traffic rules change so that the sign marking
that kind of road allows pedestrians, we don't have to edit all trunks
in a country, and
(b) it fixes the problem where someone might not be familiar enough with
the traffic rules so he doesn't know for example that pedestrians
aren't allowed and doesn't add that access tag.
We've had a similar issue like that recently on talk-be, where mappers
didn't know the exact meaning of a sign. Something tagged with a sign
for access=destination in Belgium means: no entry except to the houses
or fields in that road, and except pedestrians, cyclists and horse
riders (and a few more exceptions that don't matter here).
The "pedestrians" part is obvious to anyone over here, the latter two
aren't. Indeed, you can even find those signs now and then that have a
redundant "except bicycles" sign under it, so the people putting up
those signs aren't always aware of that either.
Now suppose that access=destination would just have the world-wide
definition so it wouldn't exclude bicycles or horse riders. If our
mappers don't know the exact meaning of the traffic sign, it would mean
that all routers would steer you round these access=destination roads.
So, therefore we can better define this by country (or perhaps state in
some cases), where the rules are actually made, so this problem won't
More information about the talk