title: Multiplex networks in metropolitan areas: generic features and local effects.
abstract: Most large cities are spanned by more than one transportation system. These different modes of transport have usually been studied separately: it is however important to understand the impact on urban systems of coupling different modes and we report in this paper an empirical analysis of the coupling between the street network and the subway for the two large metropolitan areas of London and New York. We observe a similar behaviour for network quantities related to quickest paths suggesting the existence of generic mechanisms operating beyond the local peculiarities of the specific cities studied. An analysis of the betweenness centrality distribution shows that the introduction of underground networks operate as a decentralizing force creating congestion in places located at the end of underground lines. Also, we find that increasing the speed of subways is not always beneficial and may lead to unwanted uneven spatial distributions of accessibility. In fact, for London—but not for New York—there is an optimal subway speed in terms of global congestion. These results show that it is crucial to consider the full, multimodal, multilayer network aspects of transportation systems in order to understand the behaviour of cities and to avoid possible negative side-effects of urban planning decisions.
authors.affiliation: Laboratory of Geography Information Systems (LaSig), Polytechnic School of Lausanne (EPFL), Lausanne, CH, Switzerland.
authors.forename: Emanuele
authors.initials: E
authors.lastname: Strano
authors.affiliation: School of Computer Science, University of St Andrews, St Andrews, Scotland, UK Department of Mathematics, University of North Carolina, Chapel Hill, NC, USA.
authors.forename: Saray
authors.initials: S
authors.lastname: Shai
authors.affiliation: School of Computer Science, University of St Andrews, St Andrews, Scotland, UK.
authors.forename: Simon
authors.initials: S
authors.lastname: Dobson
authors.affiliation: CEA, Institut de Physique Theorique, Gif-sur-Yvette, France EHESS, Centre d'Analyse et de Mathématique Sociales, Paris, France marc.barthelemy@cea.fr.
authors.forename: Marc
authors.initials: M
authors.lastname: Barthelemy
mesh_terms: D000465:Algorithms; D002947:Cities; D002958:City Planning; D005843:Geography; D008131:London; D015233:Models, Statistical; D009518:New York; D011890:Railroads; D014186:Transportation
keywords: multilayer networks; spatial networks; transportation; urban geography