A simple roadway control system for freeway traffic

In this paper, a roadway control system that regulates variable speed limits along the freeway in addition to ramp metering is proposed to counteract traffic congestion and improve freeway efficiency. It treats the speed limit for one freeway section as a virtual ramp meter for the downstream freeway section. The control design is only based on the fundamental flow density relationship and can be easily implemented in real-time applications. Compared with the previous roadway control systems, the proposed control system requires less modeling information and computational effort. Simulation results are presented to demonstrate the efficiency and robustness of the proposed roadway control system.