A group controller for controlling elevator cars in a building having a plurality of floors includes a traffic and traffic rate estimator for providing fuzzy estimates of traffic and traffic rate; a closed loop fuzzy logic controller for providing a control parameter in response to the fuzzy estimates of traffic and traffic rate and in response to an elevator control system output variable, the closed loop fuzzy logic controller having membership functions for fuzzy sets of the control parameter; an adaptive controller for modifying the membership functions of the fuzzy sets of the control parameter in response to the elevator control system output variable; and an elevator dispatcher for controlling the operation of the elevator cars during single source traffic conditions in response to the control parameter.