Mainstream traffic flow control on freeways using variable speed limits

Abstract

Mainstream Traffic Flow Control (MTFC), enabled via variable speed limits, is a control concept for real-time freeway traffic management. The benefits of MTFC for efficient freeway traffic flow have been demonstrated recently using an optimal control approach and a feedback control approach. In this paper, both control approaches are reviewed and applied to a freeway network in a simulation environment. The validated network model used reflects an actual freeway (a ring-road), fed with actual (measured) demands. The optimal and feedback control results are discussed, compared and demonstrated to improve significantly the system performance. In particular, the feedback control scheme is deemed suitable for immediate practical application as it takes into account operational requirements and constraints, while its results are shown to be satisfactory. In addition, the control system performance was not very sensitive to variations of the parameters of the feedback controller. This result indicates that the burden associated with fine tuning of the controller may be reduced in the field.