Combining Variable Speed Limits with Ramp Metering for Freeway Traffic Control

This paper proposes a control strategy for combining Variable Speed Limits (VSL) and Ramp Metering (RM) to maximize the flow of a recurrent bottleneck which can be modeled as a lane reduction. The control strategy can be simply described as: (a) Assuming a known ramp metering rate for each onramp; (b) using Finite Time Horizon Model Predictive Control to design VSL for each link; (3) VSL design is based on a simplified 2nd order METANET model with density (or occupancy) and mean speed as the state variables. Simulations are conducted in Matlab with several performance measures to evaluate the control strategy quantitatively.