[Talk-us] routing tags used by actual routing applications

[Kevin Broderick]

IMO (based on both the wiki and what I've seen on the map), highway=track
implies something that is not reasonably drivable by normal passenger cars
at a normal rate of travel. In Vermont, we have a whole lot of unpaved
roads that are perfectly fine at 35-45 MPH (well, except for mud season);
those seem to fit highway=unclassified or highway=residential better than
highway=track.

The routing discussion does get into a bit of sticky area that applies at
least to Vermont, New Hampshire and Massachusetts—all three have old
roadways that remain legal right-of-ways but that are not town-maintained.
Some are privately maintained to normal road standards, others are
maintained to some lesser standard (e.g. "So I can get my pickup up to
camp"), others have very little to no ongoing maintenance but get traveled
by 4x4s and dual-sport motorcycles (whose operators are likely to clear
deadfall but not to replace washed-out culverts, for example), and others
have reverted to forest or may even have been "paper roads" that were
plotted with inadequate knowledge of topography (up cliffs, etc.).
According to the wiki, those should be tagged motor_vehicle=yes because a
road-legal vehicle is *legally* allowed to travel them ("*Access values* are
used to describe the *legal* access for highway
<http://wiki.openstreetmap.org/wiki/Key:highway>=*s"), but I sure as heck
don't want to get routed down some of them when driving my Taurus. I may
very well want to get routed down them while riding my dual-sport
motorcycle or if I was out in a 4x4 truck.

As I've been updating data in Vermont, I've been relabeling
highway=unclassified or highway=residential to highway=track if it would
seem to be an unpleasant surprise while operating said Taurus, and I've
been using the somewhat debated smoothness= tag to add further data where
possible. I've also been adding in missing sections of those unmaintained
right-of-ways, usually as highway=track, that were not on the TIGER imports.

IMO, the default expected behavior of a routing system should be to avoid
highway=track unless specifically encouraged to do so by user input
(whether by selecting a particular activity or by the user putting a
waypoint on a track), and we should encourage renderers to clearly
distinguish tracks from roads.

Also IMO, any track that is at all visible on the ground and congruent with
a legal, public right-of-way, ought to be on the map. However, we do need
to tag them appropriately so that routing and rendering systems can
distinguish those ways that are legal for motor vehicles but physically
impassible for most from those that are legal and readily passable (and,
where possible, also distinguish the converse—those that are passable but
not legal ROW).


On Wed, Jul 2, 2014 at 9:11 AM, Paul Johnson <baloo at ursamundi.org> wrote:

> I would expect tracks to be in play except when explicitly excluding
> unpaved roads, barring surface tags to the contrary, otherwise as a last
> resort.  Much of the US doesn't pave county roads, yet they're often packed
> and graded to the point someone with a low slung sedan can safely do 45 on
> them.
> On Jul 1, 2014 3:37 PM, "Martin Koppenhoefer" <dieterdreist at gmail.com>
> wrote:
>
>>
>>
>> > Il giorno 01/lug/2014, alle ore 23:15, Jason Remillard <
>> remillard.jason at gmail.com> ha scritto:
>> >
>> > For example, scout does
>> > not route over highway=tracks, unless you are in pedestrian mode. It
>> > seems like a reasonable decision, perhaps all of the routers do this,
>>
>>
>> no, some routers do use tracks for car routing (I'd expect a router to
>> use tracks for cars, but only as a last resort when there are no
>> alternatives)
>>
>> In your original post you mentioned path and cycleway, those should
>> indeed not route cars
>>
>>
>> > but the wiki documentation says nothing of the sort, and it surprised
>> > me.
>>
>>
>> I'd file a bug at scout and see what they respond, you should definitely
>> not adapt osm data based on one router
>>
>>
>> cheers,
>> Martin
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-- 
Kevin Broderick
ktb at kevinbroderick.com
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