A new approach for combined freeway Variable Speed Limits and Coordinated Ramp Metering

Freeway corridor traffic flow is limited by bottleneck flow. A possible approach for maximizing recurrent bottleneck flow is to create a discharge section immediately upstream of the bottleneck. This paper proposes a control strategy for combining Variable Speed Limits (VSL) and Coordinated Ramp Metering (CRM) design to achieve this objective when the bottleneck can be modeled as a lane drop (or virtual lane drop) and/or weaving section. The control design strategy is to design VSL first and then use Finite Time Horizon Model Predictive Control to design Coordinated Ramp Metering. Microscopic simulation results showed that the control strategy could improve traffic throughput significantly.