Mainstream Traffic Flow Control of merging motorways using Variable Speed Limits

Mainstream Traffic Flow Control (MTFC), enabled via Variable Speed Limits (VSL), is a novel proposed motorway traffic management tool. An existing simple local cascade feedback MTFC controller for a single motorway is extended in this paper for application to two merging motorways. A split-range-like scheme is derived that employs VSL at both motorways simultaneously, so as to balance the experienced delay in both of them while keeping capacity-flow conditions in the merge area. The new MTFC controller remains simple yet efficient and suitable for ready field implementation. The controller is evaluated in simulation and compared to the optimal control results. The controller´s performance is shown to meet the specifications of delay balancing and to approach the optimal control results for a number of investigated scenarios.