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Reference node ID 1349143672

I was recently using the OSMAND app to navigate and it directed me to make an illegal U-Turn. (I know it is illegal because my wife was stopped by the cops for doing it. Nothing to do with OSM.)

Anyway, I thought I would look at the OSM data and try to fix this. The situation is where a dual carrigeway ends and becomes a two way road. The restriction is that a U-Turn back to the other side of the dual carrigeway is prohibited. There is currently a no_U_Turn restriction in the OSM data but I don't think that is correct. No U Turn means one is not allowed to go back on the same path. I think the restriction should be No_Left_Turn back to the other lane of the dual carrigeway.

I tried to make this change in JOSM, but the validator complained that this restriction needs to be part of a relation. That is where I am stuck. I find this business of relations to be quite difficult and have gotten into serious difficulty messing with them in the past, so I thought it best to seek some guidance on this occasion.


asked 17 Dec '19, 17:27

dougcb68's gravatar image

accept rate: 0%

This relation looks close but needs the node where you can't turn back to the other side added as a "via" node - especially in this instance where it looks like the ways join at both ends (can you do a U-turn at the other end - that would need to be a second relation with a different via node and the from and to roles swapped).

Edit: if the roadsign says no u turn then that is the restriction type to use. In practice no u turn or no left turn in this instance with the same from and to ways and via node should work the same for routing.

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answered 17 Dec '19, 17:54

EdLoach's gravatar image

EdLoach ♦
accept rate: 22%

edited 17 Dec '19, 17:56

Good! That is what I was missing. I didn't realize the node was also needed as "via" in the relationship. This passed the validator. Thanks.

(17 Dec '19, 18:27) dougcb68

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question asked: 17 Dec '19, 17:27

question was seen: 907 times

last updated: 17 Dec '19, 18:27

NOTICE: is no longer in use from 1st March 2024. Please use the OpenStreetMap Community Forum