One algorithm for controlling the order in which floors are visited for a lift is called SST or "shortest seek time first". It keeps a list of all the floors it is currently requested to visit and, after a stop, it will next visit the closest on its list. If two requests are the same distance away, it goes in the direction in which more floors have requested the lift. A lift using SST has just stopped at floor 7 and its request list contains floors 0, 4, 10, 14 and 16. Just after it starts moving, a new request comes in for floor 7.