Controlling a plurality of elevators at peak times

In order efficiently to cope with a greater traffic demand occurring at a specific service floor at a specific time zone, a plurality of elevators is split into a plurality of service groups e.g. SERV.GRP.A and SECV.GRP.B each for exclusively serving zones of specified service floors assigned respectively thereto. Traffic demand at the common service floor which is serviced by all service groups is serviced automatically depending on the traffic condition or in response to a hall call by calling an elevator car from the most appropriate service group(s), wherein the hall call buttons HB on the common service floor need not be allocated to each service group since the call is automatically processed, thereby enabling to call a most appropriate elevator car for the user from any of the split service groups flexibly and efficiently and without obliging the user to follow any specific operational instructions.