[NTC2016-SU-R-04] Sustainability and Scaling of Urban Transportation Networks

Today, urban areas are home to more than half of the world’s population, with a projected urban population of 6.3 billion (68% total global population) in 2050 (UN, 2012). The concentration of population in urban areas has positively affected the economic growth, spurring entrepreneurship, inventions, and business innovation (Bettencourt and West, 2010). In addition, large cities are often “greener” than rural areas, because people living in denser habitats typically have smaller energy footprints, require less infrastructure and consume fewer resources per capita (Kalnay and Cai, 2003; Bettencourt and West, 2011). Despite these benefits, urban areas confront a number of sustainability challenges, resulting from the complex interaction of infrastructural, economic and social components (Arnfield, 2003; Cash et al., 2003; Patz, 2005; Nazaroff, 2013). The problems associated with urban growth, however, are typically treated as independent issues with a lack of proper account of intra- /inter-city “bridging networks” via transportation systems (Figure 1). Urban economies currently generate more than 90% of global gross value added, meaning few peri-urban or rural systems are unaffected by urbanization (Seto et al., 2012). Being the ultimate urban land connectors, malfunction or under-performance of transportation networks may in fact trigger the failure of other systems as these elements are inherently interdependent (Badland and Schofield, 2005; Bettencourt et al., 2007). This issue involves complex system planning of intra- and inter-city road network and the integration of the structure, function, and evolution mechanisms of the system (Batty, 2008; Hou et al., 2015).