There’s currently a discussion regarding the tagging used for this feature (between @mueschel and myself) regarding whether toilets:wheelchair:grab_rails=yes or toilets:grab_rails=yes should be used to describe the accessibility grab rails present with a toilet, and I would appreciate more input on the matter.
In my opinion, the wheelchair namespace is inaccurate, unnecessary, and potentially misleading. I think it is inaccurate because grab rails aren’t a feature specifically intended for wheelchair users — they are simply an accessibility feature that is present around a toilet. Even if they were only for wheelchair users, the usage would be unnecessary in that case as wheelchair would then be implied by the sheer fact of its existence. It may also create an issue for misleading tagging — I can imagine a toilet existing with grab rails present, but is not wheelchair accessible (eg not large/spacious enough). If a toilet is accessible to wheelchairs, it should have a wheelchair=yes tag I think.
To me, toilets:grab_rails would indicate all toilets covered by that object have grab rails. toilets:[type]:grab_rails would indicate that specific section of the toilets have grab rails. If wheelchair is used to denote a separate accessible section exists, then toilets:wheelchair:grab_rails seems reasonable to me, as it gives us more specific data.
One could add the number of toilets that have grab rails. For example, a toilet feature that contains 5 toilets where 2 have grab rails could be tagged as follows:
amenity=toilets
toilets:number=5
toilets:grab_rails=2
What if, for example, at random, some stalls have grab rails, and some don’t, and they’re otherwise the same? I don’t see how specifying wheelchair helps to locate them in that case.
The current use of toilets:wheelchair is not necessarily about a separate section - if so, we would also need toilets:male and toilets:female (which only exist as a synonym of toilets:num_chambers).
wheelchair is just a common namespace for handicapped-friendly features. It’s used in many different contexts. As grab_rails are for the handicapped, this information belongs into this namespace.