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barrier=kerb
(1) On a way along the length of the kerb, to map the kerb itself.
(2) On a node that is part of a highway, to map the location where someone travelling along the highway has to cross a kerb. This includes situations where the highway crosses abarrier=kerb
way, but very often the kerb is not mapped separately as a way. The current version of the Wiki page contradicts itself on this usage.
I do not see the contradiction, barrier=node represents a kerb, you can draw it as a way, or mark the position punctually where it is most relevant (on a crossing footway typically).
More information about the kerb can be added by adding the kerb=* key which serves as a rough indicator of the height of the kerb and how much of an obstacle it is. For mapping the exact height of the kerb, on ways height=* is commonly used, on nodes kerb:height=*.
There is agreement that
barrier=kerb
should only be used on a node that is part of a highway if anyone travelling along the highway has to cross the kerb: therefore it should typically not be used on ahighway=crossing
or by itself on a node that is part of a road. This would imply that it applies to cars travelling along the road, like some sort of traffic calming measure.
+1
Despite this, the use of
barrier=kerb
on a road is not uncommon and it would (as of March 2023) lead to unexpected results if a data consumer was to assume that all of these slow cars down or present a significant barrier to cyclists travelling along the road.
Actually barrier=kerb on a highway is very uncommon, there are 0,2% occurences of this: https://taginfo.openstreetmap.org/tags/barrier=kerb?filter=ways#combinations
barrier=kerb on a node that is part of a highway is expected, but that it is a road highway is not, although it might occur in rare cases for driveways or similar. Did you count these situations and how many were there? Is it concentrated in specific regions?
Just because the data is not completely reliable we should not change the definition of the tag. A barrier=* should always be some sort of barrier (or hole in a barrier, as in barrier=entrance), it doesn’t make sense to add barrier=* to something to indicate a barrier somewhere else. These are just tagging noise / mistakes we should correct.
kerb=*
- On a barrier=kerb way, at the actual location of the kerb, to indicate the type or approximate height of the kerb
- On a barrier=kerb node, at the actual location of the kerb, to indicate the type or approximate height of the kerb
- By itself, on a node that is part of a path, footway, service road or similar, at the actual location of the kerb, for example where the highway crosses a kerb (though the kerb itself is often not mapped separately as a way). When encountering such a case, it makes sense to add the missing “parent tag” barrier=kerb, for clarity (so it becomes an example of usage 2)
- By itself, on a node on a road (e.g. highway=primary/secondary/…), to mean that there is a kerb on each side of the way at this point. This should not be taken to mean that someone travelling along the road has to cross the kerb, therefore adding barrier=kerb here would be wrong.
- On something like a
highway=crossing
node or ahighway=bus_stop
node. In this use it is an additional tag providing more information, liketactile_paving=yes
. It indicates that there is a kerb somewhere near this node that someone visiting the node might want to know about, but the kerb is not necessarily at the exact location of the node and this tagging therefore does not imply abarrier=kerb
orwheelchair=no
.Of these 5 different meanings, only no. 3 and 5 are currently documented in the Wiki.
I’m not proposing changes to the documentation of the different values for kerb=*, that’s another story.
to make it short:
barrier=kerb → a kerb feature
kerb=* → a property that describes a kerb or the absence of a kerb
so +1
if the kerb is already mapped as in 2, would you still think that it is recommendable to add or remove kerb=* to/from a nearby crossing node?
if the kerb is already mapped as in 1,should we recommend to add or remove barrier=kerb on/from the nodes where a highway crosses a kerb?
Cheers,
Martin