|local reference/local platform number|
|Used on these elements|
|Tools for this tag|
It is used on stop positions (public_transport=stop_position) of busses, trams and trains to indicate the number (or letter) of the corresponding platform (public_transport=platform). Add this Tag with the same value to both elements.
So it is used for the reference of one platform, as ref=* would indicate the ref of the whole stop area.
Example with three bus stops: https://www.xn--pnvkarte-m4a.de/#11.8825;51.508;18
Example with three bus stops: https://www.openstreetmap.org/#map=19/51.50814/11.88204&layers=T
Stop positions of trams and trains aren't rendered. The reason is unknown.