Road Network Traffic Congestion Evaluation Simulation Model based on Complex Network

Abstract

To deeply analyze the dynamic evolution process of traffic congestion on road network and provide policy analysis tools for traffic congestion governance, the article proposed a traffic congestion evaluation simulation model on based on complex road network. By introducing section impedance concept into complex network theories, it achieved combination of topology model and traffic model on road network. Moreover, it proposed assessment methods on road network access capacity traversing in virtual test vehicles which could assess the road access capacity under different road network. At last, on PC system, it managed complete network congestion assessment simulation system, and made simulation analysis on factors affecting the access capacity such as number of road congestion, traffic flow and road network topology. The simulation results are same with classical theoretical analysis on traffic, and could reflect more dynamic process information, which shown that the model could make traffic network congestion assessment accurately and effectively as well as provide basis for related traffic congestion management decisions. Introduction In recent years, several researching groups had conducted researches on structural analysis of traffic network. Research results of Hui Yong Et al shown that public traffic network in Shanghai and Beijing presented a structural feature of Small World and Power Law. While Zong Yueguang research further proved the complex nature of network structure in traffic network. In his doctor papers, Wu Jianjun had made systematic analysis of complex network nature of traffic network structure, while Zhang Chen Et al.had analyzed the bus line Network Topology in Shanghai and Zhang Yong Et al. had conducted further study on robustness of traffic network on the basis of traffic network complexity. Traffic Flow Simulation had become a research focus in recent years, while the existing traffic simulation research still concentrated on simulation of dynamic evolution of microscopic traffic flow, which lack of consideration of traffic network structural factors. On the other hand, most of researches on traffic network concerned more about the structural characteristics of traffic network while lacked of traffic flow consideration. Through transmission dynamics characteristics of traffic, Li Shubin Et al. had studied the impact on traffic congestion by traffic network topology. Sun H Et al. had proposed the traffic dynamic theoretical model taking traffic network topology into consideration. By making full use of computing power of calculation simulation technology, the article would base on complex network theory and by section impedance model, introduce the traffic network congestion simulating evaluation taking traffic flow into consideration to achieve fine-grained. Construction of traffic network congestion evaluation and simulation model based on complex network Complex network theory Small-World model was firstly proposed by D. Watts Et al. and was used to simulate relation of human and society. The following researches shown that many structures in human living environment could be presented by Small-World model, such as grid structure and traffic network. 6th International Conference on Machinery, Materials, Environment, Biotechnology and Computer (MMEBC 2016) © 2016. The authors Published by Atlantis Press 2107 Small-World model could be described with Figure 1. Figure 1 Small-World model of D. Watts As shown in Figure 1, Small-World Topology was a topology between rule model (as shown in left side of Figure 1) and completely random model (as shown in right side of Figure 1). In Small-World structure, sides with some proportion (Pr) would be treated in random while most sides would remain a rule structure. Random sides connected knots with distant relation, thus it is also called "Short Cut". The mean value, which defined the minimum distance between two random points in the topology, is called characteristic path of the topology. The existence of random sides significantly shorten characteristic path length of the topology. Decrease of characteristic path promoted the accessibility and connectivity of topology. In following researches, several teams had studied the information transmission and robustness of Small-World structure [12]. Results of existing researches shown that there is Small-World structure in city traffic network. In certain area, sections had close connection while different areas were connected with main lines. Sections within area are equal to rule sides of Small-World while the main lines between areas could be regarded as Short Cut side of Small-World, subject to Small-World structure, a simulation model of traffic network could be created. Section impedance model Section impedance model was used to analyze the section delay issues caused by traffic flow, including time of vehicles through section and waiting time at intersection. Section impedance model was the most common model in practice as a computing model proposed by FHWA [2], as shown in Formula 1: ttaa = ttaa �1 + αα( xxaa ccaa � )ββ� (1) Of which ta means section impedance, ta means the impedance value of section with traffic flow of 0. α and β are correction factors, in general, α = 0.15 and β = 4.0.xa means flow on section and ca means the actual accessibility of section other than the maximum accessibility. When the flow increased to ca , the related impedance value would be 1.15 times of ta. A problem lied in such model existence was that, when the traffic flow was infinitely close to section accessibility, the section impedance would not approach infinity, which is non-conformance to fact. In fact, when the traffic flow exceeded section accessibility, the section would be completed blocked, the infinity through section impedance would be regarded as the section was removed from the network. Thus, Davidson proposed a new section impedance calculation model, as shown in Formula 2[3]: ttaa = ttaa �1 + JJ( xxaa (ccaa − xxaa) � )� (2) Of which J is correction factor and ca is section accessibilty, xa ca ⁄ is general unit in traffic engineering, usually called ratio of "flow/capacity" or congestion coefficient, other symbols in formula had the same meaning with that in Formula 1. According to Formula 2, when the congestion coefficient is 1, the section impedance would approach infinity. When the traffic flow is 0, the section impedance would be ta. Compared to the impedance model of FHWA, this model could better reflect the actual flow characteristics of the section. Thus, on construction of section Increasing randomness Regular Small World Random

Original document

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• http://dx.doi.org/10.2991/mmebc-16.2016.422 under the license https://creativecommons.org/licenses/by-nc

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