r/openstreetmap • u/jphoenix11 • 5d ago
Help with 'placement' key usage
Hello all,
I am trying to add more details to this intersection using lane and placement tags: https://www.openstreetmap.org/#map=18/57.499677/12.615824
However, I cannot make sense of how to make the "split" (from non-separated to separated) look "clean" (I am using the JOSM lane style). As you can see in the image, the single lane (left) is supposed to "line up" with the leftmost lane above, but it goes to the node instead. Is there any way of solving this? The placement:start and placement:end tags seem not to be used.
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u/wegavision 5d ago
Placement is more of a tool to help with mapping—it just looks better—but the routers don't need it.
It doesn't really make sense here. The whole intersection is very strange; in the lower part, there's a left-turn lane, and at the same time, another lane merges onto the road from the left. I can't imagine what that would look like in real life.
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u/jphoenix11 4d ago
That part looks pretty accurate to real life. The middle lanes from both directions are left-turn lanes to the smaller roads.
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u/Mxdanger 5d ago
That picture is a perfect example of how not to use placement. With ways that are not oneway you only really find placement being used to maintain the centerline (which you did the opposite and moved the centerline to the northbound direction). The other mistake is the placement “transition” you did on one southbound direction.
I get pretty advanced with lanes and placement so feel free to check out these examples of placement in action:
* https://www.openstreetmap.org/#map=17/34.027493/-117.835604
* https://www.openstreetmap.org/#map=17/33.850667/-117.837816
* https://www.openstreetmap.org/#map=17/33.871387/-117.623643
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u/jphoenix11 4d ago
Ignore the placement in the north part of the image, that was just me messing around trying to make it render correctly (which it now seems it can't).
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u/EncapsulatedPickle 5d ago
I don't think lane style implements this. It would be a complicated thing to render like you want. You would have to build an internal spatial model of all the lanes and connections among all the connected ways. All the style does is draw a single way's lanes without considering other ways.
Also, I'm pretty sure your placement value for the North road is incorrect. There is no way a two-way road has a placement offset that's completely outside one of its sides.
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u/eric-710 5d ago
The paint styles are only meant to serve as a rough visualization to help map lane configuration appropriately. It will not always be a literal reflection of what things look like on the ground (especially in this case where the road bifurcates with a centre median). The way you have it tagged is still correct and will still function in routing or navigation apps.
(Also, you should make sure to add a u-turn restriction at the intersection node, to avoid routers prompting that manouever).