Graded speed limit control strategy under highway congestion

YU Xue; FENG Pengfei; DUAN Mengmeng

doi:10.3969/j.issn.1672-0032.2025.05.003

Abstract：To alleviate occasional congestion problems after highway traffic accidents,the traffic flow states before and after accidents are simulated using the software VISSIM,and traffic flow data for non-congested and congested states are obtained.The Greenshields model and the Greenberg model are used to fit the speed-density relationship curves for non-congested and congested states,respectively,and a highway traffic congestion duration prediction model is constructed.Through the model,the congestion duration under different upstream arrival flows and different traffic accident blockage times is calculated,and the model's accuracy is verified through simulation.The highway traffic congestion duration prediction model is combined with a genetic algorithm to solve the vehicle speed when vehicles arrive at the queue tail position of the congested section,thereby determining the optimal speed limit.A graded speed limit control strategy is proposed for congestion situations,where multiple gradual speed limits are implemented for vehicles from the upstream section of the accident,allowing the speed to decrease smoothly and restricting the number of vehicles in the congested area.The results show that the mean absolute percentage error between the calculated and simulated results of congestion duration under different upstream arrival flows and different blockage times is 14.37％,indicating that the traffic congestion duration prediction model has high accuracy and can be used to calculate the congestion duration after highway accidents.After implementing the graded speed limit control strategy,when the upstream arrival flow is 3 000 veh/h,the average queue length decreases from 2 141 m to 1 340 m,and the average traffic flow speed in the congested section increases from 28.7 km/h to 36.0 km/h,demonstrating that the graded speed limit control strategy can effectively alleviate highway congestion.