Coordinated control method for freeway ramp with congestion of road section

To improve the effectiveness of heuristic control of ramp traffic on a congested roadway, an improved Bottleneck control method is proposed to obtain a stable control process and a shortened control time. First, the Greenshields model is used to determine the influence range of traffic congestion based on the distance that a shock wave travels upstream on the roadway in the congestion duration. Then, the number of ramps to be controlled coordinately is determined according to the mileposts of ramps and the influence range of traffic congestion. The traffic density is selected as the control variable to describe the congested traffic condition precisely. Finally, the levels of local control and overall coordinated control are optimized to overcome the control overshoot and extended control period of the traditional Bottleneck control method. The simulation results with traffic data measured on the Ninghang freeway reveal that compared with the traditional Bottleneck control method, the improved method can reduce the control time by 70% and decrease the overshoot by 75%.