This report introduces different coordinated traffic responsive ramp control algorithms, implemented or not-implemented, but based on promising new mathematical techniques. A total of 17 different ramp metering approaches is described. For the already implemented algorithms, the historical background, the network, the algorithm and the main references are described. The proposed ramp control approaches are briefly described and the literature references are included. Two possible directions of ramp metering for the future are qualitatively described. Based on the literature review, online simulation and fuzzy logic seem to be two very powerful approaches to be considered in the future. The hierarchic and dynamic characteristics of the online simulation ramp control system are its unique features. The on-line simulation approach is designed to handle both recurring and non-recurring congestion situations. The adaptive fuzzy logic control approach allows a fast and reliable calibration of the existing parameters and the controller adapts itself to a new environment or to changes of the traffic patterns. Two different adaptive components, neuro-fuzzy systems (ANFIS) and evolutionary strategies are introduced. KEYWORDS: Ramp Metering, Fuzzy Logic, On-line Simulation, FREQ
