Future Urban Mobility Inter-Disciplinary Group, Singapore-MIT Alliance for Research and Technology, Singapore, Singapore.
PLoS One. 2012;7(7):e40575. doi: 10.1371/journal.pone.0040575. Epub 2012 Jul 6.
Whilst being hailed as the remedy to the world's ills, cities will need to adapt in the 21(st) century. In particular, the role of public transport is likely to increase significantly, and new methods and technics to better plan transit systems are in dire need. This paper examines one fundamental aspect of transit: network centrality. By applying the notion of betweenness centrality to 28 worldwide metro systems, the main goal of this paper is to study the emergence of global trends in the evolution of centrality with network size and examine several individual systems in more detail. Betweenness was notably found to consistently become more evenly distributed with size (i.e. no "winner takes all") unlike other complex network properties. Two distinct regimes were also observed that are representative of their structure. Moreover, the share of betweenness was found to decrease in a power law with size (with exponent 1 for the average node), but the share of most central nodes decreases much slower than least central nodes (0.87 vs. 2.48). Finally the betweenness of individual stations in several systems were examined, which can be useful to locate stations where passengers can be redistributed to relieve pressure from overcrowded stations. Overall, this study offers significant insights that can help planners in their task to design the systems of tomorrow, and similar undertakings can easily be imagined to other urban infrastructure systems (e.g., electricity grid, water/wastewater system, etc.) to develop more sustainable cities.
虽然被誉为解决世界弊病的良药，但城市在 21 世纪仍需要不断适应。特别是，公共交通的作用可能会显著增加，因此急需新的方法和技术来更好地规划交通系统。本文研究了交通的一个基本方面：网络中心性。通过将中间中心性的概念应用于全球 28 个地铁系统，本文的主要目的是研究随着网络规模的发展，中心性在全球趋势中的出现，并更详细地研究几个单独的系统。研究发现，与其他复杂网络特性不同，中间中心性随着规模的增加而趋于更加均匀地分布（即没有“赢家通吃”）。此外，还观察到了两个不同的状态，它们代表了其结构。此外，中间中心性与规模呈幂律关系（平均节点的指数为 1），但大多数中心节点的中间中心性下降速度比最不中心节点慢（0.87 比 2.48）。最后，还研究了几个系统中各个车站的中间中心性，这对于定位可以重新分配乘客以减轻拥挤车站压力的车站可能很有用。总体而言，本研究提供了有意义的见解，可以帮助规划者设计未来的系统，类似的工作也可以轻松地应用于其他城市基础设施系统（例如，电网、水/废水处理系统等），以建设更可持续的城市。
