“…Graphs have been applied to many fields including engineering, electronics, social sciences, operations research (see, for example, Barnes and Harary 1983;Foulds 1992). Of most direct relevance here, graph theory has found significant application to the analysis of transport networks where there is an intuitive and obvious relationship between the links and nodes in a transport network and the edges (E) and vertices (V) in a graph G (for example, Kansky 1963;Morlok 1967;Bell and Iida 1997;Banks 1998;Buckwalter 2001;Barthélemy 2011). This conventional approach-sometimes referred to as a "primal" approach (Porta, Crucitti, and Latora 2006a)-has been used in several recent analyses of road networks (Buhl et al 2006;Cardillo et al 2006;Porta, Crucitti, and Latora 2006a;Lämmera, Gehlsena, and Helbinga 2006;Scellato et al 2006;Masucci, Stanilov, and Batty 2009;Strano et al 2012).…”