As promised I made a quick tut for animated escalator.
The keyword here is precision.
Animated escalator made from 2 identical staircases occupying the same space with cloned steps.
Y and Z values I used to animate staircases are equal to the steps length and height.
Further enhancement may include morphs for the first and last couple of steps to simulate respectively rising and lowering them (this is not covered by the tut).
Hope this helps.



Update: Somebody pointed out that it would work with just one staircase. Indeed, it will. Just animate the same way 60 frames, then save the clip, reapply it and multiply.