Useless Information

Approaching the elevators in the library today, I noticed that one of them has a sign on it that says "Please do not use." Just out of curiosity, how is it possible to use an elevator that the relevant authorities don't want used? Can't they just turn it off?

Sticking with the traditional "Out of Order" would have been better, methinks. Best policy, though: just don't put the sign up at all. There are six elevators along the row, and they don't have displays over the doors showing which floors they're on. Short of standing there for 20min. or so and paying careful attention to how often an elevator arrives at each door, there really is no way to know whether any of them are out of order.

It's kind of an interesting informatics problem, when you think about it. What is the fastest way to find out which, if any, of the elevators are out of order? But since this falls under the category of "useless information" (from the point of view of the passenger, anyway), I doubt anyone will spend much time puzzling it out. It's not as though it maximizes anyone's chances of getting where he needs to go in the fastest possible time...