In message , at 14:29:52 on
Fri, 13 May 2011, Basil Jet remarked:

The other way to exploit one shaft and motor would be to attach two
lift cages on top of each other, with the top one streetside and the
bottom one airside. If the distance between the two cages was the same
as the distance from street to ticket hall, they could both load
simultaneously at the top, although they'd need to load separately at
the bottom.

I've never seen that lift configuration, possibly because one lift's
occupants will assume they are trapped when the lift stops without the
doors opening.
--
Roland Perry