Study Of Urban Road Traffic System Based On Thermodynamics Entropy And Chaos Theory

The study of urban road traffic system,based on scientific theory and idealogy,throughanalyszing the constructure and features of the system and exploring the mechanism of theinteraction among factors forming the system and reciprocity between the system and theoutside,biuld up a variety of model fiting into practical conditions to reveal the law ofevolution of urban road traffic system.No doubt,it is very important researching on the urbanroad traffic system not only to improvment of the system self but also to development ofwhole city economy.The study of urban road taffic system is one of important research items relating totrasportation engineering。In the passed time,it had been studied more widely and deeply,according to different view points.However it is relevent rare to study it further throughmaking use of physics methods,including dynamic theory,entropy theory,and chaos theory.In this paper,different parts of urban road traffic system have been studied synthetically bymeans of physical method and thought.At first,based on the chaostic character of traffic system,this paper put forward theprinciple for the development of urban road traffic system,discussed thermodynamicsfeatures of the system,and constructed the thermodynamics entropy of it.In order to describe urban road traffic system effectively,through analysing charactersof traffic flow system,the concept of the traffic potential was established in this paper.Inaddition,the factors affecting traffic potential was discussed.At the same time,the relaventtraffic pressure was quantited by means of defination of the traffic potential grade,whichwould contribut a lot to furthermore describtion of road traffic sustem.According to thecharacters of traffic flow,the cobweb model of the supply-need relationship of urban roadtraffic system was built up,and some problems about the model was discussed on bassis ofchaos theory.On the basis of the analysis of thermodynamics entropy,this paper discussed the way tobuild up the thermodynamics entropy of traffic flow,and then established the traffic flowentropy.Through the analysis of the entropy variation of road traffic system,this paperrevealed the mechanism of the traffic flow entropy producing,and set up the equation of theentropy producing.At last,according to the entropy theory,the differentiating equation of thestate and the model of traffic flow were derived.The above method can be used widely todeal with the problem relating to traffic flow,which is meaningful to the development of traffic flow theory.Aimed at the problem of traditional traffic flow differentiating equation in theory and inpractical use,the traffic pressure was analysed synthetically,and it was pointed out that trafficpressute results from matual effect between traffic flow and road.According to the idea ofmomentum law,the traffic flow defferentiating equation based on kinetic theory was derivedthrough the introduction of relative traffic pressure and relative momentem,and the factor ofthe viscosity resistance is obtained.Under practical conditions of road and traffic flow,Greenshields equation and car following model were derived by means of the traffic flowdifferentialing equation.The results show that the traffic flow differentiating equation isunitive in theory,clear in concept,and overcome the disadvantage of the man-identified factorof viscosity resistance,which is meaningful to the development of traffic flow theory.Based on the principle of sustainable development,this paper put forward the principleof urban road network layout.Through further analyzing,this paper proposed effectioncoefficients of urban road network layout,and finally established the equation for theevaluation of urban road network layout.The results show that the method is feasible inpractice.In order to reflect the reliability of urban road network objectively,on the basis of theanalysis of urban road network structure and function,it was put forward that OD roadnetwork consists of main roads and connection roads.According to the principle of reliabilityengineering,the relative influence factors on the reliability was analyzed,and the method ofthe reliability calculation was studied.Based on the main roads reliability,the reliabilityequation of OD road network was derived through introducing OD connectivity.Theinfluence of the node number on OD road network reliability and the method of how toimprove OD road network reliability were discussed further.Analysis and calculation resultsshow that the reliability of the OD road network is 0.621 when main roads are not connectedeffectively,the reliability will be 0.704 through the connection of main roads when thecontinuance of main road is not influnced.It was indicated that the reliability of OD roadnetwork depends on not only the continuance and the validity of main road but also theconnectivity of OD road network,so this method is feasible and effective.In order to predict chaotic time series of traffic flow accurately,according to theprinciple of chaotic attractor,this paper analyzed correlativity between the central phase pointand the neibour phase point in the region of chaotic attractor,and pointed out that thecorrelativity plays an important role in the prediction.Making use of the principle and method of grey system,this paper obtained the correlativity weight,and established the forecastmodel with the correlativity weight.At last,incorperating distance weight and correlativityweight as synthetic weight,this paper derived the one-order linear prediction model withsynthetic weight and established the multi-dimensional forecast model of chaotic time seriesof traffic flow.The analyzed result shows that it is feasible and effective.This paper pointed out the shortcoming of the original grey relation analysis method inranking of influnece factors,which may cause the tendence controlled by relation value ofparticular points and make some useful information lost.In order to overcome theshortcoming,through introducing grey entropy and connecting it with grey relation degree,this paper established the coincidence degree.The applicaton of practical example showsthat the ranking order of thanspoetation factor based on the coincidence degree method isbasically accord with based on others,so it is feasible.