Elevator swing car assignment to plural groups

An elevator system has a low rise group of floors and a high rise group of floors and a swing car 16 having doors and car call buttons enabling it to operate in either the low rise or high rise, the swing car 16 being assignable to one of the other rise depending upon the burden, but also being able to accept calls in the other rise in response to a variety of characteristics of traffic within the elevator system. In one embodiment, the swing car 16 is always assigned at the lobby to the low rise but proceeds into the high rise in response to hall calls therein; the swing car 16 can accept down calls in the low rise if there is a high burden in the low rise or a down call has been waiting for a long time, or if the car has a very light load. Dedicated cars 15,17 may be shut down and only the swing cars 16 used at nights and on weekends. At nights and on weekends, the high rise and low rise can be effectively merged into a single system served by swing cars, thereby to save energy in light traffic.