A. Hegyi, B. De Schutter, and H. Hellendoorn, "Model predictive control for optimal coordination of ramp metering and variable speed control," Proceedings of the 1st European Symposium on Intelligent Technologies, Hybrid Systems and their implementation on Smart Adaptive Systems (EUNITE 2001), Tenerife, Spain, pp. 260-272, Dec. 2001.
We apply model predictive control to optimally coordinate variable speed limits and ramp metering. The basic idea is that speed limits can increase the (density) range in which ramp metering is useful. For the prediction we use a slightly adapted version of the METANET traffic flow model that takes the variable speed limits into account. The optimal control signals aim at minimizing the total time that vehicles spend in the network. The coordinated control results in a network with less congestion, a higher outflow, and a lower total time spent. In addition, the receding horizon approach of model predictive control results in an adaptive, on-line control strategy that can take changes in the system automatically into account. We illustrate our approach using a simple network for which we compare the cases 'ramp metering only' and 'coordinated ramp metering and speed limits' for a typical demand scenario.