Freeway shockwave control using ramp metering and variable speed limits

In this work a novel controller design method is suggested for motorway shockwave management using ramp metering and variable speed limit (VSL) control. The proposed controller has a feedforward-feedback control structure that is designed for a motorway arterial model. For the feedback design the nonlinear model predictive control is used. The feedforward control is utilized to enhance the operability of the control system to high disturbances. Two different controllers are designed: while controller A uses continuous VSL signs, VSL input values of controller B is chosen from a discrete set. For the latter, a two-step optimization is used to decrease oscillations. The designed controllers are tested in a case study, in which a total traffic breakdown situation is modeled. In the uncontrolled case, the initial perturbation leads to a traffic jam with zero traffic speed, whereas the proposed control design is capable of preventing the congestion.