A new coordinated, traffic-responsive ramp metering algorithm has been designed for Minnes ota's freeways based on density measurements, rather than flows. This is m otivated in view of recent research indicating that the critical value of density at which capacity is observed is less sensitive and more stable than the value of capacity, thereby resulting in more effective control. Firstly , we...

A System-Wide Adaptive Ramp Metering (SWARM) system has been implemented in the Portland, Oregon metropolitan area, replacing the previous pre-timed ramp-metering system that had been in operation since 1981. SWARM has been deployed on six major corridors and operates during the morning and afternoon peak hours. This report presents results of a " before " and " after " evaluation of the perfor...

This study uses regression analysis to evaluate long-run traffic management system performance. Three important traffic management systems in the Twin Cities metro area—Ramp Metering, Variable Message Signs, and Freeway Service Patrols (the Highway Helper Program) were evaluated using multiple regression models to predict link speed and incident rate. We find that ramp meters increase freeway l...

An efficient ramp control strategy may not be politically attractive due to its negative impacts on equity. This paper addresses this issue and presents a new objective for ramp metering—minimizing weighted travel time—which is able to balance efficiency and equity. A quasioptimization/simulation approach is used to achieve the new objective. BEEX, a new family of control strategies with variou...

This paper treats the problem of optimizing a coordinated ramp metering strategy based on a distributed macroscopic traffic model. The Lighthill, Whitham and Richards (LWR) model is extended to include on/off-ramps with on-ramp flow saturations and an optimal control formulation is proposed. Using optimization techniques in Banach spaces, a solution is shown to exist and the necessary optimalit...