Cooperative systems based control for integrating ramp metering and variable speed limits

Abstract

Traffic congestion leads to significant economic and environmental costs. Currently, we can reduce congestion using infrastructure based systems, such as ramp metering installations and variable speed limits. However, we see more and more in-vehicle technologies which have the potential of replacing infrastructure based technologies. Therefore, in the future we will be able to reduce congestion by controlling individual vehicles using cooperative systems based control strategies. In this thesis we will develop a cooperative systems based control strategy to resolve a moving jam near an on-ramp. This strategy determines the number of vehicles that should be speed limited to resolve a moving jam with respect to a certain ramp metering rate. Additionally, vehicles are speed limited to realize a stable traffic flow once the moving jam has been resolved. The control strategy is evaluated using a simulation of traffic on a one-lane freeway on which all vehicles are equipped with ideal cooperative systems. The most important findings of this research are: (1) that a moving jam near a metered on-ramp can be resolved, thus resulting in an improvement of the throughput, and (2) that the most optimal throughput improvement is achieved when choosing a ramp metering rate which is as low as possible. The control strategy is one of the first integrations of ramp metering and variable speed limits for cooperative systems which can reduce congestion. However, before this system can be implemented in practice, the control system has to be able to deal with more complex traffic networks and non-ideal cooperative systems.