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🍃 Organic Maps is a free Android & iOS offline maps app for travelers, tourists, hikers, and cyclists. It uses crowd-sourced OpenStreetMap data and is developed with love by MapsWithMe (MapsMe) founders and our community. No ads, no tracking, no data collection, no crapware. Please donate to support the development!
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Unauthorised U-turn #9178

Open Kamerijker opened 3 months ago

Kamerijker commented 3 months ago

*Describe the issue Routing by car proposes an unauthorised U-turn on a primary road in Halle, Belgium https://www.openstreetmap.org/

Schermafbeelding 2024-08-31 om 14 13 42

System information:

RedAuburn commented 3 months ago

route: https://www.openstreetmap.org/directions?engine=fossgis_osrm_car&route=50.741319%2C4.239185%3B50.738304%2C4.235981#map=17/50.740143/4.236587

biodranik commented 3 months ago

Are u-turns prohibited in the osm data?

Bugsbane commented 3 months ago

I don't know. What I do know is that routing frequently suggests U turns where it is not safe to do so, ie on large, major roads. Really this shouldn't happen anywhere larger than a residential street.

map-per commented 3 months ago

It looks like OM suggests the U-Turn at the connection of two OSM road segments right next to, but not at the intersection.

Are u-turns prohibited in the osm data?

For some reasons there are no_u_turn restrictions in the OSM data. Usually, however, no_u_turn are only added on intersections and not on free track sections.

biodranik commented 3 months ago

@vng is it easy to filter out such u-turns on connected segments?

vng commented 2 months ago

Well, we should definitely filter U-turns on single roads (without other connections) even if they are split on several ways.

@Kamerijker I see that you have started adding no-u-turn relations. Well, not a problem here, but it looks like mapping for the app :) We should resolve it in a better way in the code, since there are 3 more same points in this particular intersection. Actually, a better OSM fix here is to merge 3 ways into one, especially when they have identical tags.

BTW, Graphhopper has the same bug.

Kamerijker commented 2 months ago

@vng yes i did add u-turn relations hoping some routers would pick those up, but found out later that most routers are ignoring these relations and use other algorithms to avoid u-turns, and yes GraphHopper has still the same problem even after my changes. OSRM and Valhalla are doing the right job here.

muralito commented 2 months ago

I don't know. What I do know is that routing frequently suggests U turns where it is not safe to do so, ie on large, major roads. Really this shouldn't happen anywhere larger than a residential street.

The problem is how to determine if it is safe or no to do an U turn. Maybe in an urban area you are right, but E.g. if i am driving on a quiet primary road in a rural area, for some reason i miss the intersection to turn right, the router should instruct me to do an U-turn, and not to continue driving several km until i can go back. At least is what i expect from the router.

Kamerijker commented 2 months ago

@vng the new OM version I downloaded from the Apple store today didn’t pickup my no-u-turn relations in OSM, so the U-turn problem persist.

Kamerijker commented 1 month ago

@vng the most recent OM update I installed today solved this problem. Many thanks to the support team!

map-per commented 1 month ago

Reopening as adding turn restrictions in the OSM database is not a proper fix. The OM routing should also work without these superfluous turn restrictions.