Coordination of controlled intersections and on-ramp metering

When congestion occurs on a highway in an urban environment, an effective strategy is to use ramp metering. Ramp metering postpones or prevents a traffic jam on the highway and has proven to be an effective method. On the other hand, road users on the urban road may experience more delay because they are queuing the on-ramp, or delay occurs because the queue reaches and blocks the first upstream intersection. Even when taking this delay into account, the net result of the ramp metering is positive.

Currently, the focus is to switch on the ramp metering when intensities on the highway pass a certain threshold and to switch it off when the queue on the ramp reaches the upstream intersection. Clearly, the urban road operator would like to have as much traffic as possible flowing to the highway to relieve the urban network, whereas the highway operator would like a small inflow to keep the highway free from congestion. These two different interests play an important role in the “Praktijkproef Verkeersmanagement Amsterdam”.

In this study, this is tested in practice to which extent the total road network performance in Amsterdam can be improved when dynamic traffic management measures are coordinated rather than working stand-alone or having conflicting objectives. This study focuses around a part of the Amsterdam urban road network with some controlled intersections connected to a highway where the ramps are metered. The objective is to find a method to coordinate the controlled intersections in such a way that the total time spent in the network is minimized, while imposed boundary conditions are respected. These boundary conditions can be a maximum outflow to the highway (ramp metering) or another part of the urban network (regular signal intersection control), or a minimal inflow from the highway or another part of the urban network.

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