The Analysis For The Non-Monotonicity Feature Of Traffic Assignment Paradx

With the development of national productivity levels and the improvement of people's living standards,the number of private car has increased year by year.Traffic congestion has become increasingly serious,and reasonable traffic planning is imminent.In real life,the existence of traffic paradox often further aggravates the traffic congestion.Therefore,avoiding or solving traffic paradox cannot be ignored in traffic planning and design.This paper mainly studies the non-monotonicity feature of paradox based on the different traffic assignment principles.The purpose of this paper is to explore the positive significance of the paradox links,so as to provide new ideas and theoretical support for improving the efficiency of road network.First of all,the paper gives the definition of the paradox link and the non-monotonicity of the traffic assignment paradox from two angles.The paradoxes in traffic assignment is often caused by marginal improvement of a link(marginal reduction of link's travel cost)or the addition of a new link.If marginally improving the link increases the network's total travel cost,but if the improvement degree is increased,the total travel cost of the road network will decrease,and the paradox will not occur,we can say the traffic assignment paradox is non-monotonic with link-improvement;or the addition of a new link will increase the total travel cost of the road network,but adding two identical links at the same time will reduce the total travel cost of the road network,then this phenomenon can be called the traffic assignment paradox is non-monotonic with link-addition.Then,by constructing the corresponding road networks,this paper discusses the non-monotonicity feature of the traffic assignment paradox based on user equilibrium(UE),stochastic assignment and stochastic user equilibrium(SUE).For the circumstance of improving an existing link,this paper analyzes the change of the total cost of the network with respect to the travel cost of the improved link,and concludes that the total travel cost has a non-monotonic relationship with the travel cost of link;For the other circumstance of adding new links,it is found that the toal travel cost is not monotonous with the number of new paradox links.Although this non-monotonic relationship occurs under the above three assignment principles,the reasons are also different,which mainly relate to the structure of the road network and the characteristics of the assignment principle.Finally,a real road network in Harbin is used to to verify the previous arguments,and the non-monotonic characteristics of the paradox in the two cases(improving the road section and adding new road sections)are further verified under the condition of considering the congestion effect.It is found that this phenomenon still exists in the real road network.This paper not only analyzes the characteristics of paradox from a new perspective,but also provides new ideas for the avoidance or elimination of paradox.