[Routing] Fixing routing with tags

[Florian Lohoff]

Hi,

Prolog:
Discuss a generic tag for reducing/increasing route-weights/costs regardless
of other tags.


For 10 years i am running Routing Quality Assurance by calculating
routes every 30 minutes and watching their changes over time.

When i add regions to that monitoring i typically go through 
and fix "static errors" where road taggings cause small side roads
to be used as shortcuts.

Most of the time fixing tagging on the roads and the shortcut fixes
the issue. I typically tag maxspeed, lanes, surface, lane_markings etc.

But sometimes i have cases where these tags are not sufficient and i
dont get the relative weight of the routes to the higher class 
road network.

I am missing a generic tag to influence routing in ways like "dont use
this road as a through road although legally allowed" e.g. make it
more expensive in routing.

Examples:

The route uses "Im Kracht" where it should stay on K22 and L775:
https://www.openstreetmap.org/directions?engine=fossgis_osrm_car&route=52.2340%2C8.5138%3B52.2381%2C8.4837#map=15/52.2354/8.4993&layers=N

The route uses "Westerweg" but it should stay on K27, L876, L803:
https://www.openstreetmap.org/directions?engine=graphhopper_car&route=52.2803%2C8.6965%3B52.2890%2C8.7094#map=15/52.2825/8.7106&layers=N


Dont get into discussions why one engine gets it and the other doesnt.
We are not talking about routing engine/profile comparisons. I can
create such a problem in ANY engine and profile just depending on the
geometries and tags understood in one or the other engine/profile.


So my idea would be to create a tag like **relative_route_cost=** or
the like which is a float between 0 and 2 where "1" is "use the route
weight calculated from your route engines physical tag analysis".

So 

0 -> decrease cost of this road to "0%"
1 -> Let the cost be the cost of the engines tag analysis
2 -> double the cost of the engines tag analysis

This would allow us to directly influence the usage of "shortcuts" or
through roads used "accidentally".

I would like to not create "routing engine specific" tags like
**osrm:relative_weight=** or something.

Thoughts?

Flo
-- 
Florian Lohoff                                                     f at zz.de
  Any sufficiently advanced technology is indistinguishable from magic.
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