Abstract：This study presents an improved algorithm for the clustering coefficient in a metro network model. The algorithm is based on the information transfer efficiency that considers the differences between the directly and indirectly connected origin-to-destination stations. The algorithm was evaluated using 52 metro networks in the world. The information transfer efficiency based clustering coefficients for the 52 metro networks are between 0.195 and 0.407 (average 0.29), which is lower than the value given by P-Space (Space-of-Stops), but still considerably higher than the values for random networks (0.01 to 0.16, the average is 0.06) with the same size. Therefore, metro networks are small-world networks, although with a stricter evaluation model.
王志如, 苏国锋, 梁作论. 基于信息传递效率的地铁网络小世界特性评价[J]. 清华大学学报（自然科学版）, 2016, 56(4): 411-416.
WANG Zhiru, SU Guofeng, LIANG Zuolun. Information transfer efficiency based small-world assessment methodology for metro networks. Journal of Tsinghua University(Science and Technology), 2016, 56(4): 411-416.
 Watts D J. Small worlds:The dynamics of networks between order and randomness[J]. Biometrics, 2000, 56(1):323-328.
 Seaton K A, Hackett L M. Stations, trains and small-world networks[J]. Physica A:Statistical Mechanics and Its Applications, 2004, 339(3):635-644.
 Latora V, Marchiori M. Is the Boston subway a small-world network?[J]. Physica A:Statistical Mechanics and Its Applications, 2002, 314(1):109-113.
 汪涛, 方志耕, 吴卉, 等. 城市地铁网络的复杂性分析[J]. 军事交通学院学报, 2008(2):24-28. WANG Tao, FANG Zhigeng, WU Hui. An analysis of complexity of subway network in China[J]. Journal of Academy of Military Transportation, 2008(2):24-28.
 何大韧, 刘宗华, 汪秉宏. 复杂系统与复杂网络[M]. 北京:高等教育出版社. 2009. HE Daren, LIU Zonghua, WANG Binghong. Complex Systems and Complex Networks[M]. Beijing:Higher Education Press, 2009. (in Chinese)
 DING Yiming, DING Zhou. The small-world hierarchical modularity of urban subway networks[C]//Proceeding of IEEE Conference on Computer Application and System Modeling. Taiyuan:IEEE, 2010:427-431.
 HAN Chuanfeng, LIU Liang. Topological vulnerability of subway networks in China[C]//Proceeding of IEEE Conference on Management and Service Science. Wuhan:IEEE, 2009:1-4.
 LI Wei, CAI Xu. Empirical analysis of a scale-free railway network in China[J]. Physica A:Statistical Mechanics and Its Applications, 2007, 382(2):693-703.