China's high-speed rail network construction and planning over time: a network analysis

Based on the construction scale of China's high-speed rail network (CHSRN) between 2007-2017, this paper presents the evolution process and network characteristics over this period. Additionally, according to China's latest national railway planning proposal - "The Mid- and Long-term Railway Network Plan" issued in 2016, the development prospects and impacting factors of future CHSRN from 2018 to 2030 are analyzed. The evolutionary process and regularity of CHSRN development is evaluated with various complex network measures. It is found that the degree and eccentricity of each Tier 1 city increase over time, but the pagerank of almost all Tier 1 cities decreases from 2007-2017 to 2018-2030, and that the contribution of the Tier 1 cities to the network connections decreases from 2007 to 2030. The Chinese government would be adopting an egalitarian model to construct the CHSRN in the long-term. Moreover, during the second period, the CHSRN would form increasingly more connections between more populated Tier 2 and Tier 3 cities. From 2018-2030 the clustering coefficients of some Tier 2 and Tier 3 cities would be greater than those of Tier 1 cities. The HSR planners of China may have expected a larger share of passenger flows from the Tier 1 cities to Tiers 2 and 3 cities in the future.