Research On Moving Bottleneck Of Heavy Trucks Driving On Freeways Based On Cellular Automata

In our country,the proportion of heavy trucks on the freeway is relatively high,and the problem of overloading is serious.The speed,acceleration and braking performance of heavy trucks are much lower than that of cars,which results in the formation of moving bottlenecks and deterioration of traffic conditions.Therefore,it is of great significance to study the moving bottleneck effect of heavy trucks.Aimed at the shortage of NaSch model,considering the difference of the power performance and braking performance between trucks and cars,as well as the formation mechanism of the moving bottlenecks,the moving bottleneck model of heavy trucks is founded.Aiming at the problem that the effect of moving bottlenecks is greatly exaggerated when two heavy trucks driving abreast on the two lanes,the discrimination rules and elimination rules of parallel bottlenecks are founded.After verified the validity of the proposed model,the influence of traffic density,truck proportion and truck performance on the moving bottleneck effect is analysised,the effect of lane restriction strategy on improving the traffic condition is studied,the main research results are as follows.(1)With the increase of traffic density,there are three traffic phases in heterogeneous traffic flow: free flow,synchronized flow and wide moving jam,and there are two critical densities between three traffic phases.With the increase of truck proportion,two critical traffic densities will not change;with the improvement of truck performance,two critical traffic densities decrease.(2)The higher the proportion of trucks,the stronger the moving bottleneck effect.With the increase of truck proportion,traffic flow decreases,and the higher traffic density,the more significant decrease of traffic flow;traffic congestion aggravates,and the higher traffic density,the more significant aggravation of traffic congestion;the average speed of free flow decreases significantly;the lane-change frequency of cars increases first and then decreases;the average speed and the lane-change frequency of cars change little in the synchronized flow state and the wide moving jam state.(3)The better the truck performance,the weaker the moving bottleneck effect.As the truck performance improving,traffic flow in the condition of moderate traffic density improves significantly,traffic flow in the condition of too high or too low traffic density changes little;the average speed of free flow increases significantly;the lowest density at which traffic jam occurs becomes smaller;the lane-change frequency of cars decreases significantly in the free flow state.(4)After the implementation of lane restriction,traffic flow increases;the average speed of two lanes exists significant difference in the free flow state,;congestion rate decreases,the lowest density at which traffic jam occurs becomes bigger;the lane-change frequency of cars decreases significantly in the free flow state.The higher the truck proportion,the more obvious the effect of lane restriction.