Something that I have wondered about from time to time is the problem of where an elevator rests when not in use. I suppose that for a small building it's pretty much a moot point, but what about bigger buildings (say, 5+ stories)? The way I figure, there are three basic options:
1. When not in use, the elevator can go to the main floor (or, without loss of generality, the top floor) and wait until needed.
2. When not in use, the elevator can go to the middle floor (splitting the difference).
3. The elevator can remain at the last floor it went to until it is needed again.
All three options presuppose that each floor has an equally likely chance of having the elevator summoned to that floor. Of course, if the "population" of the building is not uniformly distributed, this would skew the chances accordingly. (You'd think, also, that people on the 2nd or 3rd floor would not be as likely to take the elevator as they would the stairs, but I continue to be amazed at the number of people who get on the elevator and press "2".)
So, what do elevator programmers do? Do they actually bother figuring out which floor is most likely to have people using the elevator, and use that floor as a resting place? Or, do they just make it go to the main floor regardless?
Just off the top of my head, I would think that the elevator should go to the middle floor, figuring that that position would result in a minimal average wait time for whoever is stuck waiting for the elevator.