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 2^nd 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.