[pedoh]

At the beginning of the day, assume most people are going up from the ground floor. At lunch time, you've got a balance of people going down to the ground floor to get lunch and people going up from the ground floor post-lunch. At the end of the day, most of the people are going down to the ground floor to leave at the end of the day. And at all times you've got deliveries that initiate from the ground floor.

Have your bank of elevators start with a simple "best guess" algorithm, and then learn how to improve that algorithm. If the last employee of the building is ready to leave at 11pm, there's no reason the elevator shouldn't be at that floor waiting after a learning period.