Evolution Analysis Of Traffic Oscillation In Simple Road Networks With Different Topology

Traffic oscillation is a very common traffic flow phenomenon.In the oscillation traffic flow,vehicles can not keep running smoothly and need to accelerate and decelerate constantly,which will increase the fuel consumption and exhaust emissions of vehicles,and bring greater safety risks.The increasing amplitude of traffic oscillation may also lead to traffic congestion.Therefore,it is of great theoretical significance and application value to clarify the mechanism of the generation and evolution of traffic oscillation.Most of the existing studies focus on the traffic oscillation in the traffic flow of the road section.On one hand,it reveals the important role of driving behavior（i.e.carfollowing and lane changing）in the process of the generation and evolution of traffic oscillation.On the other hand,it is found that the back and forth propagation of traffic waves between merge and diverge structures may also cause different types of traffic oscillation in the traffic network.This paper focuses on the second type of traffic oscillation mentioned above.In this paper.the evolution characteristics of traffic oscillation are studied for different topological structures of road network.The analytical results of traffic shock evolution are derived by theoretical analysis and verified by numerical simulation.The main research work of this paper is as follows:First,the study on the evolution characteristics of traffic oscillation in a dual-path road network are carried,and the influence of the capacity of the downstream section on the evolution of traffic oscillation is analyzed.It is found that with the increase of the capacity of the downstream sections,the traffic oscillation mode zones show a decreasing trend:when the traffic capacity of the downstream section is less than the critical valuec₁,there are 11 zones;when the traffic capacity of the downstream section is between the critical value c₁ and c₂,the oscillating mode partition is reduced to 9;when the traffic capacity of the downstream section is greater than c₂,the oscillating mode partition is further reduced to 7.The critical value and the analytical results of the boundary of each oscillation mode are derived.Next,the situation where one of the routes in the dual-path road network has an on-ramp is considered,the effect of on-ramp flow on the evolution of traffic shocks is studied,and the influence of on-ramp flow on traffic shock patterns and zoning is revealed.It is found that when the on-ramp capacity is less than the critical value （?）₁,there are 11 traffic shock mode zones;when the on-ramp traffic capacity is between （?）₁ and （?）₂,the traffic shock mode zones are reduced to 9;when the on-ramp traffic capacity is greater than （?）₂,Shock mode partitions are reduced to 8.Similarly,the critical value and the analytical results of the boundary of each oscillation mode are derived.Finally,the evolution characteristics of traffic oscillation in a three-path road network are studied,and two scenarios are analyzed.In Scenario 1（2）,the two paths have the same distributary ratio and the same traffic capacity and are larger（smaller）than the third path.It is found that in scenario 1,the result is the same as that of the two-path road network,and there are 9 traffic shock modes.In Scenario 2,the traffic shock pattern is reduced to 6 zones.The research results reveal the effect of road network topology on the evolution of traffic oscillation,which can provide a scientific basis for further proposing reasonable traffic management and control measures to alleviate traffic oscillations.