A. Hegyi, B. De Schutter, and J. Hellendoorn, "Optimal coordination of variable speed limits to suppress shock waves," Proceedings of the 7th TRAIL Congress 2002 - TRAILblazing into the Future - Selected Papers (P.H.L. Bovy, ed.), Rotterdam, The Netherlands, pp. 197-220, Nov. 2002.
We present a model predictive control (MPC) approach to optimally coordinate variable speed limits for highway traffic. A safety constraint is formulated that prevents drivers from encountering speed limit drops larger than, say, 10 km/h is incorporated in the controller. The control objective is to minimize the total time that vehicles spend in the network. This approach results in dynamic speed limits that reduce or eliminate shock waves. For the prediction of the evolution of the traffic flows in the network, which is needed for MPC, we use an adapted version of the METANET model that takes the variable speed limits into account. The performance of the discrete-valued and safety constrained controllers is compared with the performance of the continuous-valued unconstrained controller. It is found that both types of controllers result in a network with less congestion, a higher outflow, and a lower total time spent. For our benchmark problem, the performance of the discrete controller with safety constraints is comparable to the continuous controller without constraints.