Footways in subway stations should be tagged with `key:tunnel`?

In general subway stations should be considered buildings, tunnels or both?

I don’t mean the volume around rails where the trains move.
I mean the set spaces, on different levels, where normal citizen are allowed to walk,
the facilities like amenities and shops accessible inside, the stairs and elevator connecting them.
I checked very few samples and many seems to be tagged as tunnels.

The question come from this MapRoulette challenge: (about this way: osm, indoorequal)

I should remove the tunnel=yes tag or add something like layer=-2;-1 on top of level=-2;-1?

For reference:

The pedestrian area is not coverd. They are moving though a set of below ground buildings/rooms. The station should be mapped as a set of buildings with a negative layer. The pedestrian ways should then travel through those rooms.

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as this way does not cross with any physical object (only administrative boundary) layer tag is meaningless

(“this is underground” is expressed by location=underground - not by negative layer tag, layer tags only say about ordering of crossing objects)

Do you have photo of that place? For me it looks like it can be described as indoor covered tunnel, but describing it as corridor in an underground building also may work.

(not entirely sure would I use tunnel and covered - and whether adding covered=yes to indoor=yes ways makes sense)

Ways within a building I’d consider corridor and also the level=* tag plus or minus. If a straight thru passage tunnel=building_passage is also worth considering. Gard du Nord has is a fine example where it was kept KISS, highway=footway+indoor=yes+level=0

It’s still unclear because then you have to ask whether the =subway is tunnel=yes when it goes through the station box, when the =footway around are indoor=yes
Furthermore a station can be connected with many tunnels and adits. They are difficult to be treated as indoor= with level= in a building= . So the extent and consistency can be debated, despite the possibility that a building= can be connected with bridges and tunnels.

I tried to look more deeply into the documentation related to subway stations but I haven’t found definitive answers (and it seems there was a lot of discussions about the general topic of metro mapping)

So I looked at what is already present on the map.
Possible options are:

  1. both area and footpath are tunnel and indoor
    i.e.: footway, area, indoorequal
    or: footpath, area, indoorequal
  2. footpath is tunnel and indoor, area is indoor but not tunnel (i.e. footpath, area, indoorequal)
  3. footpath is indoor but not tunnel, area is indoor and tunnel (i.e. footway, area, indoorequal)
  4. both footpath and area are only indoor and not tunnel
  5. other


  • indoor means having tags indoor=* and level=-<x>
  • tunnel means having tags tunnel=yes and layer=<x>

The most common cases in Europe seem to be 1. and 2. so for consistency I assume that:

  • footpath inside underground spaces should be tagged as tunnels

Even if I haven’t found documentation about this tagging and I find counterintuitive.

Open question:

  • Which areas are tunnel which are only indoor spaces If there are criteria to distinguish which underground areas (closed ways) part of a subway station are tunnels and which are only indoor space please feel free to link them.
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