On Fri, 13 May 2011, Roland Perry wrote:

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.

You could have a sign outside the window saying DON'T WORRY, YOU ARE NOT
TRAPPED, perhaps. Or, if there was an intermediate level the same distance
below the ticket hall as that is below the street, the doors could open
there. You could even furnish such a level merely to prevent distress!

On double-decker lifts more generally:

http://en.wikipedia.org/wiki/Double-deck_elevator

tom

--
These spoiled youths forget that when they are shaven they look like
boiled potatoes. -- Tara Singh