Connectivity Contribution to Urban Hub Network Based on Super Network Theory – Case Study of Beijing
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Yuan G, et al. Connectivity Contribution to Urban Hub Network Based on Super Network Theory – Case Study of Beijing GUANG YUAN, Ph.D. candidate1,3,4 Traffic Planning E-mail: [email protected] Original Scientific Paper DEWEN KONG, Ph.D.1,3,4 Submitted: 4 Mar. 2020 E-mail: [email protected] Accepted: 6 July 2020 LISHAN SUN, Ph.D.1,3,4 (Corresponding author) E-mail: [email protected] WEI LUO, Ph.D.2 E-mail: [email protected] YAN XU, Ph.D.1,3,4 E-mail: [email protected] 1 Beijing Key Laboratory of Traffic Engineering Beijing University of Technology 100 Ping Le Yuan, Chaoyang District Beijing, 100124, China 2 Beijing University of Civil Engineering and Architecture No.15 Yongyuan Road, Daxing District Beijing, 00044, China 3 Beijing Laboratory for Urban Mass Transit 100 Ping Le Yuan, Chanoyang District Beijing 100124, China 4 Engineering Research Center of Digital Community Ministry of Education, 100 Ping Le Yuan Chanoyang District Beijing, 100124, China CONNECTIVITY CONTRIBUTION TO URBAN HUB NETWORK BASED ON SUPER NETWORK THEORY – CASE STUDY OF BEIJING ABSTRACT KEYWORDS With the rapid development of urbanization in China, super network; super-edge; transportation hub; the number of travel modes and urban passenger trans- connectivity. portation hubs has been increasing, gradually forming multi-level and multi-attribute transport hub networks in 1. INTRODUCTION the cities. At the same time, Super Network Theory (SNT) has advantages in displaying the multi-layer transport In recent years, the process of urbanization has hubs. The aim of this paper is to provide a new perspec- had a leap-forward development in China, and nu- tive to study connectivity contribution of potential hubs. merous modes of transportation have emerged to Urban transport hubs are ranked through topological meet the people’s growing demands for travelling, features based on Hub Super Network (HSN). This paper which has improved the urban quality of life and proposes two indexes based on Super-Edge (SE), Zero urban operational efficiency [1]. At the same time, Hub Degree of SE (ZHDoSE) and a number of shared multimodal traveling makes people converge at SEes (NSSE), respectively. Then, a case study was con- multimodal transfer points, which brings pressure ducted in Beijing, which considers four combinations to to the transfer hubs in a city. Moreover, frequent oc- study the influence of transport modes and subway lines on connectivity. The results show that no-normalization currence of incidents has directly affected people’s strengthens the contribution of transport modes and sub- travels and commutes, even the economic develop- way lines on connectivity. Besides, the transport mode ment. Recently, scholars [2–6] have carried out the contributes a lot to the connectivity. However, elements analyses of topological features that have great im- normalization strengthens the subway lines under ZH- pacts on the characteristics of a network. Therefore, DoSE reciprocal. In addition, various weights of ZH- good understanding of the topological features of a DoSE and NSSE have different influences on the recogni- network could guide hubs management operations tion results of SEes in HSN. and take preventive measures effectively. Promet – Traffic&Transportation, Vol. 33, 2021, No. 1, 35-47 35 Yuan G, et al. Connectivity Contribution to Urban Hub Network Based on Super Network Theory – Case Study of Beijing Of course, like many topological networks in and Line 14 includes Beijing south railway station), transportation [6–11], the features of urban hubs have which shows that a single node in a complex network been studied before by complex network in which the will ignore two subway lines in Jiulongshan subway urban hubs are taken as single nodes. As urban hubs station. Therefore, new indices should be proposed to contain several transport modes, the single complex represent the features since node degree cannot de- network has defects in performing multimodal urban scribe the connectivity of a multi-level hub network. hubs. However, the multimodal network hub is much Transport modes and subway lines have great ef- more complicated than single transportation hubs fects on the efficiency of multi-layer transport hubs. on complex network. More specifically, the hub has Therefore, a new index combined with the number of multiple transport modes and multiple track lines in a transport modes and the number of subway lines is node, which means multi-tier attributes in the nodes. presented in this paper. Furthermore, the transfer hub includes various facil- Though features of the complex network have ities of several transport modes and connections of been a hot topic with the widespread application on different facilities, which increases the complexity transportation [15–18], it is difficult to describe the and difficulty in performance analysis on complex characteristics of multi-layer travel hub networks. networks. In addition, the complexity is also brought Meanwhile, the concept of Super Network Theory by the increasing number of hubs and spatial distribu- (SNT) was firstly proposed by Sheffi in 1985 [19], tion in a city. Hubs network will lose more multi-di- and then, it was defined by professor Nagurney as mensional information when the hubs are simplified the network of a network [20]. Up to the present, by a single complex network. Therefore, the urban the SNT has the advantage of providing new per- hub network has the characteristics of multi-dimen- spectives and methods and has been widely applied sion, multi-level, multi-attribute, and multiplicity. It in many fields [21–24]. Of course, some applica- will lose much information when being analysed us- tions can be also found in the field of transportation ing a single network. For example, nodes just show [25, 26]. However, it is rarely mentioned from the one transport mode and link, failing to represent the perspective of urban transportation hubs. The SNT relationship between travel modes and layers. The can bring new elements with multi-dimensional at- characteristics of urban hubs that are formed by the tributes and describe nodes and links multi-dimen- overlaying of several transport modes cannot be fully sionally. Besides, new elements proposed in SNT reflected by a single network. The study on hubs with carry a lot of information; for example, the connec- multiple transport modes is rarely mentioned in the tions between multi-layer nodes and multi-dimen- previous research. Therefore, there is an urgent need sional connection of a single node. Therefore, the for a multi-dimensional method or model to interpret SNT has great potential in exploration and applica- the structure of urban hubs and study the characteris- tion in the field of urban hubs. tics. Then, it can provide guidelines for steps to im- Based on the existing research, this paper at- prove operational efficiency, enhance service capaci- tempts to build a multi-layer model by SNT and ty, and then reduce the economic losses. provide appropriate indices to describe the connec- Hub transmission efficiency is an important index tivity properly. The SNT model can provide a new to evaluate hub services, and high connectivity be- perspective for urban hub network and new ele- tween hubs is an important guarantee for hub effi- ments. In this paper, multi-dimensional indicators ciency. The connectivity has a great relationship with are obtained and more information is represented by node degree in complex networks [12–14]. Many new elements. The paper then explores how trans- studies have done this before and achieved fruitful port modes and subway lines contribute to the con- results. However, most of the research lacked effec- nectivity of the urban hub network. According to tive modelling and analysis of urban hub networks, SNT, the framework of urban Hub Super-Network ignored the importance of transport modes and edge (HSN) is built and new elements are presented. Be- characteristics in multi-level hub networks. For in- sides, due to the uncertainty of combination, several stance, passengers plan to leave Beijing by trains. combinations of transport modes and subway lines The passenger has fewer options in Beigongdaxi- are discussed, and parameters are also discussed men subway station (Line 14 contains Beijing south based on the HSN. The case study has been con- railway station) than the one in Jiulongshan subway ducted in Beijing city. Hence, the main purpose of station (Line 7 includes Beijing west railway station this paper is to explore the influence of the number 36 Promet – Traffic&Transportation, Vol. 33, 2021, No. 1, 35-47 Yuan G, et al. Connectivity Contribution to Urban Hub Network Based on Super Network Theory – Case Study of Beijing of transport modes and the number of subway lines Sub-nodes that are labelled 0 are assigned to on connectivity. This knowledge could be utilized sub-network: due to the lack of certain mode(s), the to provide useful guidance for urban transport hub hub nodes cannot reveal the intact vertical relations operations and managements. between sub-nodes in corresponding sub-networks. This paper is organized as follows. In the next For instance, the Beijing west railway station does Section, the HSN methods are described. In Section not have an airport travel method, which means the 3, the case study is conducted, and the results are corresponding sub-nodes in the airport sub-network presented. In the Section of the discussion, factors are missing. Therefore, nodes with label 0 are in- affecting the connectivity are analysed. In the last troduced to build the connection between sub-net- Section, conclusions are drawn. works if the corresponding sub-node is missing. The sub-nodes labelled 0 are allocated to each 2. METHODS sub-network layer. In general, label 0 represents the 2.1 Assumptions missing modes of transportation in HSN.