Talk:Barriers

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Routing: a highway crossing a linear barrier

This is a routing question: if a highway crosses a linear barrier on a node with no tags, what are the routing rules? Example: a footway crosses a wall. The junction node has no tags at all. Is the routing through this node is possible? I think the response is not obvious and we should decide a rule for routing engines. --Oligo 22:58, 29 December 2012 (UTC)

My assumption would have been that these cases should not influence routing. I would even go so far as to always issue warnings to mappers due to the ambiguity, though - there should always some a tag on common nodes of barriers and highways, even if it's just a barrier=entrance indicating a gap in the barrier. --Tordanik 11:14, 30 December 2012 (UTC)

I completely agree this tagging is incorrect and validators should raise the issue (I deliberately kept the old wording which sounded like a strong recommendation). But my point was really about routing: if, as a data consumer, I encounter this case, should I route through the untagged node? I wondered if we could define a default behavior, in the same way we define defaults for node barriers (I suppose routers do use these defaults when access is not overridden). --Oligo 14:24, 30 December 2012 (UTC)

Defining default application behaviour when encountering "incorrect" mapping isn't really commonplace in OSM as far as I can tell. But if we want to document it, I would suggest taking the "does not influence routing" route because this is what developers are likely doing today anyway. --Tordanik 19:34, 31 December 2012 (UTC)

Barrier stacks

I've removed the recent addition of a recommendation to map barriers on top of each other using the semicolon value separator. I do not consider this syntax a good choice because it isn't intuitive that it indicates the vertical order of features - it could also be interpreted to represent barriers that share the same physical space (e.g. a fence inside a hedge). Probably it is also not immediately clear whether to order the values from top to bottom or from bottom to top. So even though I would like the ability to map and render this, no solution is obvious enough to be silently added to the page during a larger edit imo. --Tordanik 11:04, 30 December 2012 (UTC)

Ok. My intend wasn't to tell the relative position of features (yes it would be very difficult to deal with all possibilities). It was just to tell that a barrier may have multiple features. We could only remove the example which was misleading... --Oligo 14:37, 30 December 2012 (UTC)