Adjacent areas and overlapping segments

This is a newbie question. I am sorry if it’s evident…

I find that in many situations two areas are adjacent. E.g.:

It seems to me that the more natural way to map this would be to draw two closed areas with one (or more) shared segments, buts JOSM complains about it. What should I do? Is there any convention bout it?


Ignore the warning. What you’re doing is fine. However, you say “shared segments”, but that’s not really the case. You’re sharing a few nodes between two closed ways, but otherwise they’re completely independent. They’re not sharing a segment.

For some, the proper way to map this is to use a multipolygon relation and have a single shared way between the two areas as a member of type=outer, and the rest of the outlines of the areas also as type=outer members of their respective relations. I think it’s overkill for your case.