In view of the problem that the multimodal transport network is vulnerable to attack and faces the risk of cascading failure,three low polarization linking strategies considering the characteristics of the multimodal ...In view of the problem that the multimodal transport network is vulnerable to attack and faces the risk of cascading failure,three low polarization linking strategies considering the characteristics of the multimodal transport network are proposed to optimize network robustness.They are the low polarization linking strategy based on the degree of nodes(D_LPLS),low polarization linking strategy based on the betweenness of nodes(B_LPLS),and low polarization linking strategy based on the closeness of nodes(C_LPLS).The multimodal transport network in the Sichuan-Tibet region is analyzed,and the optimization effects of these three strategies are compared with the random linking strategy under random attacks and intentional attacks.The results show that C_LPLS can effectively optimize the robustness of the network.Under random attacks,the advantages of C_LPLS are obvious when the ratio of increased links is less than 15%,but it has fewer advantages compared with B_LPLS when the ratio of increased links is 15%to 30%.Under intentional attacks,as the ratio of increased links goes up,the advantages of C_LPLS become more obvious.Therefore,the increase of links by C_LPLS is conducive to the risk control of the network,which can provide theoretical support for the optimization of future multimodal transport network structures.展开更多
To explore the structural characteristics and vulnerability of multimodal transport networks,this study identifies the structural characteristics of a multimodal transport network on the basis of the complex network t...To explore the structural characteristics and vulnerability of multimodal transport networks,this study identifies the structural characteristics of a multimodal transport network on the basis of the complex network theory.Key nodes are clarified from the analysis of the structural characteristics.The characteristic path length and percentage of the largest subgraph are applied to analyze the vulnerability of the multimodal transport network after random and intentional attacks on the nodes.The network of a multimodal transport company is taken as an example in the empirical analysis.Results show that with more than ten nodes under a random attack,the percentage of the largest subgraph is less than 20%,and the characteristic path length is less than 2.The same performance is observed for more than seven nodes under an intentional attack.The multimodal transport network is more vulnerable under an international attack against key nodes.The results of the topology and node failure under random or intentional attacks would support the management of the multimodal transport network.Suggestions for the emergency transportation organization of enterprises under attacks are proposed accordingly.These suggestions should help improve network invulnerability and recovery from node failure.展开更多
In this paper,computational models of environmental pollution and energy consumption of urban multimodal traffic network are proposed according to pertinent research and a multi-objective programming model is then dev...In this paper,computational models of environmental pollution and energy consumption of urban multimodal traffic network are proposed according to pertinent research and a multi-objective programming model is then developed to formulate optimization problem for such a system.Simultaneously,the main factors,such as travel time,pricing and convenience which influence travelers' choice behaviors are all considered and a combined assignment model is proposed to simulate travelers' mode and route choices.A bi-level programming model,in which the multi-objective optimization model is treated as the upper-level problem and the combined assignment model is processed as the lower-level problem,is then presented to solve multi-criterion system optimization problem for urban multimodal traffic network.The solution algorithms of the proposed models are also presented.Finally,the model and its algorithms are illustrated through a simple numerical example.展开更多
There is an explicit and implicit assumption in multimodal traffic equilibrium models, that is, if the equilibrium exists, then it will also occur. The assumption is very idealized; in fact, it may be shown that the q...There is an explicit and implicit assumption in multimodal traffic equilibrium models, that is, if the equilibrium exists, then it will also occur. The assumption is very idealized; in fact, it may be shown that the quite contrary could happen, because in multimodal traffic network, especially in mixed traffic conditions the interaction among traffic modes is asymmetric and the asymmetric interaction may result in the instability of traffic system. In this paper, to study the stability of multimodal traffic system, we respectively present the travel cost function in mixed traffic conditions and in traffic network with dedicated bus lanes. Based on a day-to-day dynamical model, we study the evolution of daily route choice of travelers in multimodal traffic network using 10000 random initial values for different cases. From the results of simulation, it can be concluded that the asymmetric interaction between the cars and buses in mixed traffic conditions can lead the traffic system to instability when traffic demand is larger. We also study the effect of travelers' perception error on the stability of multimodal traffic network. Although the larger perception error can alleviate the effect of interaction between cars and buses and improve the stability of traffic system in mixed traffic conditions, the traffic system also become instable when the traffic demand is larger than a number. For all cases simulated in this study, with the same parameters, traffic system with dedicated bus lane has better stability for traffic demand than that in mixed traffic conditions. We also find that the network with dedicated bus lane has higher portion of travelers by bus than it of mixed traffic network. So it can be concluded that building dedicated bus lane can improve the stability of traffic system and attract more travelers to choose bus reducing the traffic congestion.展开更多
基金The National Key Research and Development Program of China(No.2018YFB1601400)。
文摘In view of the problem that the multimodal transport network is vulnerable to attack and faces the risk of cascading failure,three low polarization linking strategies considering the characteristics of the multimodal transport network are proposed to optimize network robustness.They are the low polarization linking strategy based on the degree of nodes(D_LPLS),low polarization linking strategy based on the betweenness of nodes(B_LPLS),and low polarization linking strategy based on the closeness of nodes(C_LPLS).The multimodal transport network in the Sichuan-Tibet region is analyzed,and the optimization effects of these three strategies are compared with the random linking strategy under random attacks and intentional attacks.The results show that C_LPLS can effectively optimize the robustness of the network.Under random attacks,the advantages of C_LPLS are obvious when the ratio of increased links is less than 15%,but it has fewer advantages compared with B_LPLS when the ratio of increased links is 15%to 30%.Under intentional attacks,as the ratio of increased links goes up,the advantages of C_LPLS become more obvious.Therefore,the increase of links by C_LPLS is conducive to the risk control of the network,which can provide theoretical support for the optimization of future multimodal transport network structures.
基金The Science and Technology Demonstration Project of Multimodal Freight Transport in Jiangsu Province(No.2018Y02).
文摘To explore the structural characteristics and vulnerability of multimodal transport networks,this study identifies the structural characteristics of a multimodal transport network on the basis of the complex network theory.Key nodes are clarified from the analysis of the structural characteristics.The characteristic path length and percentage of the largest subgraph are applied to analyze the vulnerability of the multimodal transport network after random and intentional attacks on the nodes.The network of a multimodal transport company is taken as an example in the empirical analysis.Results show that with more than ten nodes under a random attack,the percentage of the largest subgraph is less than 20%,and the characteristic path length is less than 2.The same performance is observed for more than seven nodes under an intentional attack.The multimodal transport network is more vulnerable under an international attack against key nodes.The results of the topology and node failure under random or intentional attacks would support the management of the multimodal transport network.Suggestions for the emergency transportation organization of enterprises under attacks are proposed accordingly.These suggestions should help improve network invulnerability and recovery from node failure.
基金supported by the National Natural Science Foundation of China (Grant Nos. 71071016, 70901005)the Fundamental Research Funds for the Central Universities (Grant Nos. 2009JBM040 and 2009JBZ012)funded by a Discovery Grant (Application No. 342485-07) from the Natural Science and Engineering Research Council (NSERC), Canada
文摘In this paper,computational models of environmental pollution and energy consumption of urban multimodal traffic network are proposed according to pertinent research and a multi-objective programming model is then developed to formulate optimization problem for such a system.Simultaneously,the main factors,such as travel time,pricing and convenience which influence travelers' choice behaviors are all considered and a combined assignment model is proposed to simulate travelers' mode and route choices.A bi-level programming model,in which the multi-objective optimization model is treated as the upper-level problem and the combined assignment model is processed as the lower-level problem,is then presented to solve multi-criterion system optimization problem for urban multimodal traffic network.The solution algorithms of the proposed models are also presented.Finally,the model and its algorithms are illustrated through a simple numerical example.
基金Supported by the National Basic Research Development Program of China under Grant No. 2012CB725401, Fundamental Research Funds for the Central Universities under Grant No. 2012JBZ 005, Funds for International Cooperation and Exchange of the National Natural Science Foundation of China under Grant No. 71210001, National Natural Science Foundation of China under Grant No. 71271023, Foundation for the Author of National Excellent Doctoral Dissertation of China under Grant No. 201170, and Beijing Nova Program under Grant No. 2009A15
文摘There is an explicit and implicit assumption in multimodal traffic equilibrium models, that is, if the equilibrium exists, then it will also occur. The assumption is very idealized; in fact, it may be shown that the quite contrary could happen, because in multimodal traffic network, especially in mixed traffic conditions the interaction among traffic modes is asymmetric and the asymmetric interaction may result in the instability of traffic system. In this paper, to study the stability of multimodal traffic system, we respectively present the travel cost function in mixed traffic conditions and in traffic network with dedicated bus lanes. Based on a day-to-day dynamical model, we study the evolution of daily route choice of travelers in multimodal traffic network using 10000 random initial values for different cases. From the results of simulation, it can be concluded that the asymmetric interaction between the cars and buses in mixed traffic conditions can lead the traffic system to instability when traffic demand is larger. We also study the effect of travelers' perception error on the stability of multimodal traffic network. Although the larger perception error can alleviate the effect of interaction between cars and buses and improve the stability of traffic system in mixed traffic conditions, the traffic system also become instable when the traffic demand is larger than a number. For all cases simulated in this study, with the same parameters, traffic system with dedicated bus lane has better stability for traffic demand than that in mixed traffic conditions. We also find that the network with dedicated bus lane has higher portion of travelers by bus than it of mixed traffic network. So it can be concluded that building dedicated bus lane can improve the stability of traffic system and attract more travelers to choose bus reducing the traffic congestion.
