[Tagging] Strange routing

[Gregory Williams]

On Sat, 2021-10-09 at 11:44 +0200, Niels Elgaard Larsen wrote:
> https://www.openstreetmap.org/directions?engine=graphhopper_car&route=37.67318%2C22.71953%3B37.67229%2C22.71972#map=17/37.67410/22.71817
> 
> https://agol.dk/osm/issues/corinth-argos-routing.png
> 
> Am I missing something here?
> Or is it a grashopper and Osmand bug?
> 
> The only_straight_on seems correct.
> 
> I drove here and Osmand had the same problem as Grasshopper.
> 
> 
Agreed that the tagging looks fine to me. I also note that the
no_u_turn seems to be being ignored (or treated as the exact opposite)
if I move the start point slightly further north:

https://www.openstreetmap.org/directions?engine=graphhopper_car&route=37.67406%2C22.71950%3B37.67245%2C22.71967

Interestingly, I also see that in that routing the routing line shown
cuts diagonally SE->NW across the junction, and that seems to reflect
the position of node 828449365 one version earlier (v10 @ 2021-07-02)
than present (v11 @ 2021-10-06).

I also see that the only_straight_on relation that I think you're
referring to was only created on 2021-10-06:

https://www.openstreetmap.org/relation/13296318/

I don't know how often GraphHopper or Osmand update their routing data
from the OSM original, but I'd hazard that it could have been last
updated earlier than 2021-10-06, which is quite recent.

This isn't necessarily the reason for the issue, but I think it ought
to be considered.

Gregory