A hierarchy control strategy for coordinated ramp metering

The coordinated ramp metering depending on the traffic conditions in the whole freeway system rather than the local conditions around independent on-ramps have gained the most respect to ameliorate the freeway traffic situation. In this paper, a hierarchal control strategy for the coordinated ramp metering which tries to perform adequately in the varying traffic conditions is proposed. There are three control layers in this hierarchal control architecture: the direct control layer for the local ramp metering to benefit the controlled freeway section, the coordinated control layer via adaptive fuzzy considering the multi-ramp freeway traffic to determinate the nominal values used by directed layer and the adaptive layer including prediction of the possible congestion, assignation of the parameters of the controller based on the considered freeway traffic characteristics in real time. To illustrate the efficiency and feasibility of the proposed control strategy, the detailed design for the controller involving the predictive algorithms to foresee the traffic future condition, migration genetic algorithm to tune parameters of fuzzy controller, and the optimal control to local ramp metering is implemented for the loop freeway system.