Core and critical cities of global region airport networks

Citation

Lordan, O., & Sallan, J. M. (2019). Core and critical cities of global region airport networks. Physica A: Statistical Mechanics and its Applications, 513, 724-733.
doi: https://doi.org/10.1016/j.physa.2018.08.123

Abstract

Air transport is one of the key infrastructures of today’s global economy. Connections between airports define airport networks, where nodes are cities served by airports, connected by edges if there is at least one direct flight connecting them. The aims of this research are to relate structural properties of airport networks which explain how these networks respond to isolation of critical nodes, and to gain insight into relevant socio-economic factors that influence the development of airport networks. We split the world airport network (WAN) into seven global region airport networks (GRANs), using the divisions established by OAG database. We gather information about structural properties of each GRAN determining core cities through k-core decomposition, and critical cities through robustness analysis. We find that differences of robustness across GRANs can be explained by the fraction of core cities relative to total cities. Furthermore, analysis of multilevel structure reveal relevant differences between GRANs, rooted on geographical and socio-economic factors, and give insight about how network robustness in airport networks can be enhanced.

Heuristics of node selection criteria to assess robustness of world airport network

Citation

Soria, M., Lordan, O.; Sallan, J. M. (2017). Heuristics of node selection criteria to assess robustness of world airport network. Chinese Journal of Aeronautics, 30(4), 1473-1480.
doi: http://dx.doi.org/10.1016/j.cja.2017.04.012
UPCommons: http://hdl.handle.net/2117/108021

Abstract

The world airport network (WAN) is one of the networked infrastructures that shape today's economic and social activity, so its resilience against incidents affecting the WAN is an important problem. In this paper, the robustness of air route networks is extended by defining and testing several heuristics to define selection criteria to detect the critical nodes of the WAN. In addition to heuristics based on genetic algorithms and simulated annealing, custom heuristics based on node damage and node betweenness are defined. The most effective heuristic is a multi-attack heuristic combining both custom heuristics. Results obtained are of importance not only for advance in the understanding of the structure of complex networks, but also for critical node detection.

Cascades tolerance of scale-free networks with attack cost

Citation

Chen Hong, Nai-Yu Yin, Oriol Lordan, Ning He, Jose M Sallan (2017). Cascades tolerance of scale-free networks with attack cost. International Journal of Computational Intelligence Systems,  10(1):1330-1336.

UPCommons: http://hdl.handle.net/2117/109280

Abstract

Network robustness against cascades is a major topic in the fields of complex networks. In this paper, we propose an attack-cost-based cascading failure model, where the attack cost of nodes is positively related to its degree. We compare four attacking strategies: the random removal strategy (RRS), the low-degree removal strategy (LDRS), the high-degree removal strategy (HDRS) and the genetic algorithm removal strategy (GARS). It is shown that the network robustness against cascades is heavily affected by attack costs and the network exhibits the weakest robustness under GARS. We also explore the relationship between the network robustness and tolerance parameter under these attacking strategies. The simulation results indicate that the critical value of tolerance parameter under GARS is greatly larger than that of other attacking strategies. Our work can supply insight into the robustness and vulnerability of complex networks corresponding to cascading failures.

Robustness of airline route networks

Citation

Lordan, Oriol; Sallan, Jose M; Escorihuela, Nuria; Gonzalez-Prieto, David (2015). Robustness of airline route networks, Physica A: Statistical Mechanics and its Applications, 445:18-26.

doi: http://dx.doi.org/10.1016/j.physa.2015.10.053

Abstract

Airlines shape their route network by defining their routes through supply and demand considerations, paying little attention to network performance indicators, such as network robustness. However, the collapse of an airline network can produce high financial costs for the airline and all its geographical area of influence. The aim of this study is to analyze the topology and robustness of the network route of airlines following Low Cost Carriers (LCCs) and Full Service Carriers (FSCs) business models. Results show that FSC hubs are more central than LCC bases in their route network. As a result, LCC route networks are more robust than FSC networks.

Analyzing the multilevel structure of the European airport network

Citation

Oriol Lordan, Jose M. Sallan (2017). Analyzing the multilevel structure of the European airport network. Chinese Journal of Aeronautics, 30(2):554-560.

doi: http://dx.doi.org/10.1016/j.cja.2017.01.013

Abstract

The multilayered structure of the European airport network (EAN), composed of connections and flights between European cities, is analyzed through the k-core decomposition of the connections network. This decomposition allows to identify the core, bridge and periphery layers of the EAN. The core layer includes the best-connected cities, which include important business air traffic destinations. The periphery layer includes cities with lesser connections, which serve low populated areas where air travel is an economic alternative. The remaining cities form the bridge of the EAN, including important leisure travel origins and destinations. The multilayered structure of the EAN affects network robustness, as the EAN is more robust to isolation of nodes of the core, than to the isolation of a combination of core and bridge nodes.

Dynamic robustness of the European air transport network

Citation

Melgosa, M., Lordan, O. Sallan, J. M., Fernandez, V., Gonzalez-Prieto, D. (2015). Dynamic robustness of the European air transport network. 2015 ATRS World Conference. National University of Singapore (Singapore)

Abstract

The analysis of the robustness of an air transport network (ATN) - i.e., its resilience facing the isolation of random airports (errors) and the isolation of central airports (attacks) - can be undertaken from an static or a dynamic perspective. The static perspective, that is, the impact on ATN connectivity of the long-term isolation of a set of airports, has been assessed in previous research (e.g., Lordan et al. 2014), but there are few attempts to assess the transitory effects on network connectivity of total or partial closure of one or several airports. Through simulation of the European ATN, we assess the impact of the closure of several central airports in a given moment of time, determining the fraction of cancelled flights, flight delays and assessing the possibility of cascading effects (saturation of other airports). Results shows that the European ATN is relatively robust facing the closure of a single airport. Future research aims to assess other consequences of total or partial airport closure (e.g., flight delays and delay propagation) and the impact of other ATN disruptions (closure of a flight information region or an area control center).

Robustness of regional air transport networks

Citation

Lordan, O., Sallan, J. M., Fernandez, V.; Gonzalez-Prieto, D. (2015). Robustness of regional air transport networks. 2015 ATRS World Conference. National University of Singapore (Singapore)

Abstract

The aim of this study is to compare the robustness of regional airline route networks (RARN) facing errors (random isolation of several airports) and attacks (isolation of central airports that may cause a major damage to network connectivity). Nodes of RARN are airports of a region, and there is an edge for each pair of airports connected by a direct flight (Zannin and Lillo, 2013). The regions analyzed are Africa, Asia, Australasia, Caribbean, Central America, Europe, Middle East, and North and South America. It has been proven that the topology of airline route networks makes them resilient to errors, but vulnerable to attacks(Guimerà et al., 2004, 2005). Robustness to errors is assessed through several simulations of random node isolation are performed, and robustness to attacks through several node selection criteria (Petreska et al, 2010). Network resilience is assessed through the decrease of the size of giant component as a function of the fraction of isolated nodes, and through a normalized vulnerability index based on edge betweenness (Boccaletti et al., 2007, Lordan et al., 2015). Results show that air global network regions have quite different values of resilience, being the Asian and European networks the more robust, and Australasia and Middle East the less resilients.

Cascading failures with local load redistribution in interdependent Watts–Strogatz networks

Citation

Hong, Chen; Zhang, Jun; Du, Wen-Bo, Sallan, Jose M; Lordan, O (2016). Cascading failures with local load redistribution in interdependent Watts–Strogatz networks. International Journal of Modern Physics C. 27(11), 1650131.

doi:  http://dx.doi.org/10.1142/S012918311650131X

Abstract

Cascading failures of loads in isolated networks have been studied extensively over the last decade. Since 2010, such research has extended to interdependent networks. In this paper, we study cascading failures with local load redistribution in interdependent Watts–Strogatz (WS) networks. The effects of rewiring probability and coupling strength on the resilience of interdependent WS networks have been extensively investigated. It has been found that, for small values of the tolerance parameter, interdependent networks are more vulnerable as rewiring probability increases. For larger values of the tolerance parameter, the robustness of interdependent networks firstly decreases and then increases as rewiring probability increases. Coupling strength has a different impact on robustness. For low values of coupling strength, the resilience of interdependent networks decreases with the increment of the coupling strength until it reaches a certain threshold value. For values of coupling strength above this threshold, the opposite effect is observed. Our results are helpful to understand and design resilient interdependent networks.

Analysis of robustness of alliance route networks

Citation

Lordan, O., Sallan, J. M.; Simo, P., Gonzalez-Prieto, D. (2014). Analysis of robustness of alliance route networks. 2014 ATRS World Conference. KEDGE Business School. Bordeaux, France

Abstract

PURPOSE
This study analyzes the robustness of the three major airline alliances (Star Alliance, oneworld and SkyTeam) route network to unintended errors and intentional attacks. Robustness is assessed in two ways: with an edge-betweenness based vulnerability scale, and with the evolution of the size of the giant component as a function of number of disconnected nodes.

METHODOLOGY
Network robustness is assessed in several ways. First, it is proposed a normalization of a multi-scale measure of the vulnerability in order to compare the performance of networks with different sizes. Second, several adaptive strategies are proposed to minimize the size of giant component with a given fraction of disconnected nodes. Together with other approaches found in the literature, a node selection criterion based on network efficiency is introduced. Finally, it is described a new procedure -the inverted adaptive strategy- for sorting the nodes in order to anticipate the breakdown of a network.

ANTICIPATED RESULTS
Results show that Star Alliance has the most resilient route network, followed by SkyTeam and oneworld. Besides, the inverted adaptive strategy based on the efficiency criterion -inverted efficiency- shows a good performance to break networks, similar or even better than the adaptive strategy based on node betweenness.

KEYWORDS
Airline alliances, route networks, robustness, airport closure.

Robustness of airline alliance route networks

Citation

Lordan, O., Sallan, J. M., Simo, P., Gonzalez-Prieto, D. (2014). Robustness of airline alliance route networks. Communications in Nonlinear Science and Numerical Simulation, 22, 587-595.
http://dx.doi.org/10.1016/j.cnsns.2014.07.019

Abstract

The aim of this study is to analyze the robustness of the three major airline alliances’ (i.e., Star Alliance, oneworld and SkyTeam) route networks. Firstly, the normalization of a multi-scale measure of vulnerability is proposed in order to perform the analysis in networks with different sizes, i.e., number of nodes. An alternative node selection criterion is also proposed in order to study robustness and vulnerability of such complex networks, based on network efficiency. And lastly, a new procedure – the inverted adaptive strategy – is presented to sort the nodes in order to anticipate network breakdown. Finally, the robustness of the three alliance networks are analyzed with (1) a normalized multi-scale measure of vulnerability, (2) an adaptive strategy based on four different criteria and (3) an inverted adaptive strategy based on the efficiency criterion. The results show that Star Alliance has the most resilient route network, followed by SkyTeam and then oneworld. It was also shown that the inverted adaptive strategy based on the efficiency criterion – inverted efficiency – shows a great success in quickly breaking networks similar to that found with betweenness criterion but with even better results.

Study of the robustness of the European air routes network

Citation

Lordan, O., Fernandez, V., Sallan, J.M. and Simo, P. (2014). Study of the robustness of the European air routes network. 4th International Conference on Logistics, Informatics and Service Science (LISS 2014). University of California – Berkeley (USA).

Abstract

The aim of this study is to analyze the robustness of the European civil European air transportation network from the perspective of the theory of complex networks. This study is based on analyzing the behavior of the network when its nodes (airports) are removed either by random errors or by deliberate attacks. The calculation of network statistical indicators as degree and betweenness distribution reveals that the flight flow network has the small-world characteristics and scale-free property. The selection of nodes on deliberate attacks is based on four centrality criteria: degree, betweenness, pagerank and eigenvector. This study aims to contribute to the understanding of the logistics network of European commercial flights, analyzing its strengths and weaknesses.

Conference presentation

This post of the Vicenc Fernandez website contains a video of the presentation at the LISS conference

Robustness of the air transport network

Citation

Lordan, O.; Sallan, J. M.; Simo, P.; Gonzalez-Prieto, D. (2014). Robustness of the air transport network. Transportation research part E: Logistics and transportation review, 68:155-163
http://dx.doi.org/10.1016/j.tre.2014.05.011

Abstract

This paper presents a methodology for the detection of critical airports (those whose isolation would cause the largest losses in network connectivity) in the global air transport network (ATN), based on simulating an attack on selected ATN airports using different adaptive selection criteria. The performances of several node selection criteria are compared, together with a new criterion based on Bonacich power centrality. The results show that most critical airports can be detected with an adaptive strategy based on betweenness centrality. The detection of such airports may help the development of contingency plans to develop an appropriate response to any airport closure.

Study of the topology and robustness of airline route networks from the complex network approach: a survey and research agenda

Citation

Lordan, O., Sallan, J. M., Simo, P. (2014). Study of the topology and robustness of airline route networks from the complex network approach: a survey and research agenda. Journal of Transport Geography, 37:112-120.
http://dx.doi.org/10.1016/j.jtrangeo.2014.04.015

Abstract

Communication via air routes is an important issue in a world organized around a web city network. In this context, the robustness of network infrastructures, e.g. air transport networks, are a central issue in transport geography. Disruption of communication links by intentional causes (e.g., terrorist attack on an airport) or unintentional (e.g., weather inclemency) could be crucial for countries, regions and even the airlines affected themselves. Policymakers and the management of airlines and alliances should be able to reduce the effects of such interruptions in order to ensure good communication through air transport (i.e., maximize the robustness of their network at a reasonable cost). The literature review of the study of air transport route networks through an analysis of complex networks has highlighted a lack of contributions to the study of the topology and the robustness of such networks which contrasts, with advances undertaken for other transport networks or communication systems. This survey suggests areas in which research should be undertaken, based on the existing literature in other areas and from three different perspectives: global route networks, airline alliances, airlines and airports so as to help towards a better understanding of air traffic and, therefore, to be able to assess the potential damage of any airport being inoperative for a continent, country or airline.