[Tagging] Wheelchair lift

[David Earl]

I can't immediately see reference to structures like I have ringed here:
   http://wiki.openstreetmap.org/wiki/File:Wheelchair_lift.jpg
It is a small platform to lift a wheelchair, usually as an alternative 
to nearby steps. Though you get them in buildings, which would usually 
be outside the scope of OSM, they are also found outdoors like this one.

Does anyone know of existing tagging for this?

I'm sure we can all think of tagging for it, but at this stage I'm more 
interested in whether anyone knows of tags *already* in use.

Thanks,
David