The idea of having two independent elevators in same shaft dates back in the 1930s, but it took modern-day technology to turn it into the reality. To make this system work and achieve intelligent control Thyssenkrupp needed to use advanced destination dispatch system.

Thyssenkrupp is comparing the efficiency of TWIN technology to four shaft elevator group. In case you decide to use TWIN you will have a one shaft less – two TWIN systems and one regular single elevator system. This means more floor space, but in case one TWIN system goes down, it means more inconvenience.

The two TWIN cabs are prevented from getting too close by a quadruple redundant safety system: intelligent allocation of calls; automatic monitoring of minimum safety distances; emergency stop function if the safety distance is breached; and automatic engagement of the safety device in the extremely unlikely event that the first three stages fail. The TWIN system has been fully certified for safety by the German TÜV inspectorate.
In my opinion the system would be very efficient in office buildings where companies reside on multiple floors and travel between few floors is required.
For more info http://goo.gl/4eYVuH
Source: ThyssenKrupp.com