[Tagging] Sidewalk tagging: one side separate, the other implied

Jeroen Hoek mail at jeroenhoek.nl
Sun Jan 17 10:22:13 UTC 2021

When refining an urban area with sidewalk information, there are two
basic strategies:

* Implicitly map them by tagging the street with sidewalk=left/right/both/no
* Explicitly map them by drawing highway=footway + footway=sidewalk, and
tagging the street with sidewalk=separate

Sometimes — for example when one side of the street has a sidewalk
separated from it by parking bays, trees, various types of greenery and
the other has it directly parallel and adjacent to it — it makes more
sense to tag only one side separately, and have the other implied.

For this the sidewalk=* key alone offers no suitable value, but a quick
glance at Overpass Turbo shows that the following combinations are used:

(Assuming a street with the sidewalk mapped separately on the left, and
implied on the right.)




>From this actual use I would conclude that the inferred rule is that
whatever sidewalk=* defines, can be overridden by sidewalk:<side>=*.

So the following sets of tags are equivalent:

sidewalk=both          ≈ sidewalk:right=yes
sidewalk:left=separate   sidewalk:left=separate

sidewalk:right=yes     ≈ sidewalk=right

sidewalk:right=yes     ≈ sidewalk=right         ≈ sidewalk=both
sidewalk:left=separate   sidewalk:left=separate   sidewalk:left=separate

(This obviously includes weird combinations that could be tagged more
succinctly or neater.)

The wiki (https://wiki.openstreetmap.org/wiki/Key:sidewalk) does not
seem to explicitly document this behaviour, but in the past year the use
sidewalk:right=separate and sidewalk:left=separate grew to roughly 5,000
each. If there are no strenuous objections I would like to go ahead and
document the above on the wiki.

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