Hierarchical dispatching control of urban traffic systems

A two-layer hierarchical structure for urban traffic dispatching control is proposed. The upper layer problem is global optimization which is solved by a central dispatching unit (CDU). It performs resource allocation in the whole system in accordance with the working conditions in the subsystems. The lower layer problem is local optimization which is solved by local dispatching units (LDUs). They perform vehicle routing functions within the respective subsystems. Special procedures, suitable for on-line control, are proposed for obtaining the upper layer solutions and for the information exchange between the layers. The behaviour of a taxi system is simulated and the positive influence of the upper layer is shown.