Integrated Variable Speed Limit and Ramp Metering Control Against Jam Waves -- A COSCAL v2 Based Approach

In the recent past, numerous Variable Speed Limit (VSL) approaches have been designed to resolve traffic jams on the freeway. In this work, the theory of one such VSL strategy -- COoperative Speed Control ALgorithm (COSCAL v2) -- is analytically extended for integration with Ramp Metering (RM), based on traffic flow theory. COSCAL v2 is a reactive feedback VSL strategy that resolves jam waves using shockwave theory. However, on-ramp flows (with or without RM) are currently not included in its design. When VSLs are activated by jams near an on-ramp, the additional merging flow can reduce effectiveness of the VSL scheme, by preventing jam resolution or even triggering new jams in the controlled section. The integrated approach improves effectiveness of the VSL strategy, and overall network efficiency. The extended theory is evaluated for a freeway section with an on-ramp in micro-simulation, and results indicate a lower total time spent as compared to the original algorithm.