[OSM-talk] Highway=trunk : harmonization between countries ?

Fernando Trebien fernando.trebien at gmail.com
Fri Feb 23 21:38:10 UTC 2018

On Fri, Feb 23, 2018 at 5:25 PM, Mark Wagner <mark+osm at carnildo.com> wrote:
> Which one is the "best"?  If it's the fast route, there's no issue:
> both roads are already "highway=motorway".

I think the fastest route is almost always what most people would
consider the best. The exception (probably rare/non-existent in the
US) would be when the fastest route has infrastructure problems - say,
it is a dirt road - while there are nearby routes with fewer problems
(say a paved road that takes a little extra time because it is
significantly longer).

That being an exception, the local community can the discuss the
exception (in the forum, so that it can be linked to from the map) and
vote against making it the main route.

> Fargo and Rapid
> City are both larger than any city within 200 miles, which would
> seem to make them "large/important", but even by western American
> standards, they're pretty small in an absolute sense.

I propose that place=* implies importance. Fargo has 105k inhabitants
(place=city), Rapid City has 67k inhabitants (place=town). One highway
class would connect cities (city-city), a lower class would connect
towns and above (town-town, town-city), so the class of the ways
making up the route between those places would be of the second class.
If cities are connected by trunk and towns by primary, then the route
between them would be primary.

Now, which is the best route? Google insists on going through
McIntosh, whereas Here.com and Waze prefer going through Sioux Falls
or Dickinson depending on which direction you're going (mostly because
the roads in the area are nearly a grid, which is a characteristic of
the US that is not typical of most countries - that's worthy of some
discussion). Nonetheless, there are few options to choose from. Google
is the dissonant view, so maybe it should be initially ignored. The
route through Sioux Falls is part of other routes between pairs of
towns (say Sioux City - Grand Forks), so it must be a town-town route
for at least that other reason. The remaining question then is whether
the route Dickinson - Rapid City should be a town-town route.
Dickinson has 17k inhabitants, so it is a town, so that route should
be a town-town route. Which one is the main route between Fargo and
Rapid City is then not relevant because both options are town-town
routes for other reasons. If the situation did not allow us to ignore
the problem, the next step would be to collect data (tracklogs), or
publicly agree that both routes should be considered important because
they're too similar (one possible improvement for the method).

It should be noted that the route between Sioux Falls and Fargo would
end up being classified as a city-city route because it is part of the
main route between Kansas City (place=city, 459k people) and Winnipeg
(place=city, 705k people).

What if going through McIntosh is really the main route, or if all
three routers are wrong? In that case, the initial analysis would be
incorrect and the community would need to discuss that particular case
and document it. It is possible that routers in the OSM ecosystem
(OSRM, GraphHopper) can be used as long as relevant properties
(maxspeed=*, and in places with deficitary infrastructure, surface=*)
of route alternatives are mapped in OSM so that the routers can take
them into account.

What if, instead of the US, one is mapping in the UK, where place=* is
defined according to public ordinances. In that case, the method still
works, it just will judge a place's importance using another criterion
instead of population.

> Trunk, primary,
> or secondary?
> --
> Mark
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Fernando Trebien
+55 (51) 9962-5409

"Nullius in verba."

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