In message , at 15:55:08 on
Tue, 15 Jan 2013, Basil Jet remarked:
It's because the natural 'angle' of escalators and stairs are different,
due to the different step dimensions. The landings are needed to keep
the two in synch.

I think you might have put the cart before the horse... I think the
step size of escalators is deliberately different to the step size of
steps in order to ensure that a flight of escalators and multiple
flights of steps with landings can occupy the same shaft.

That might be plausible if the only escalators anywhere were the ones on
the tube, but they exist elsewhere, and have the same basic geometry as
the tube escalators, without the need to synch up with a step/landing/
step/landing scheme.
--
Roland Perry