[Tagging] Railway tagging: detail key

[Nathan Case]

Hi all,

I've noticed substantial use (99,297 instances) of the "detail" key, but 
it is undocumented on the Wiki.

Nearly all uses (99.96%) of this key are detail=track [1], which is 
associated with railways [2]. The key is predominantly used in France 
(77.6% of uses [3]) but also elsewhere across central Europe.

I have concerns about this key (it's ambiguous and perhaps redundant if 
all "correct" uses are for the same value) but, nevertheless, it would 
be good to document its usage if possible. I haven't found anything in 
the railway=*, railways, or OpenRailwayMap/Tagging documentation [4,5,6].

Does anybody know the background to this key, or what its intended 
values might be?

Many thanks,

Nathan


[1] https://taginfo.openstreetmap.org/keys/detail#values

[2] https://taginfo.openstreetmap.org/keys/detail#combinations

[3] https://overpass-turbo.eu/s/1nzc

[4] https://wiki.openstreetmap.org/wiki/Key:railway

[5] https://wiki.openstreetmap.org/wiki/Railways

[6] https://wiki.openstreetmap.org/wiki/OpenRailwayMap/Tagging