中国“四纵四横”高铁网络可达性综合评估与对比

传统测算可达性的方法较为单一，缺乏多层面、多角度的综合研究和对比分析。基于时间、经济与重心视角利用可达性模型并结合ArcGIS 空间分析手段探究高铁通车前后沿线城市可达性的动态变化；利用综合变异系数、层级分析法和改进的哈夫模型分析高铁可达性空间演变特征及规律，构建高铁可达性评价体系并结合熵权法定量评估各高铁可达综合实力。研究表明：京广、京沪可达综合实力最强，沪昆、杭福深次之，沪汉蓉、哈大、青太再次之，郑西、兰新可达实力最弱；全国高铁可达性强弱变化呈明显地带性规律，东、中部高铁可达性强于东北，东北强于西部，纵向高铁强于横向；经济潜力的增加率明显高于加权平均旅行时间的减少率，可达性重心偏移驱使不同等时圈蔓延交叠；高铁以“核心—核心”逐步向“核心—网络”空间链接模式过渡，产生上海、北京、广州、深圳4 个高铁“国家服务中心”，天津、武汉、重庆等6 个“大区域服务中心”，形成“多中心”高铁服务格局以及日益庞大而复杂的高铁特质空间集群；高铁网络影响下的中国区域空间格局的渐变与重塑日趋复杂，“T”型轴带呈现出由空间极化向空间均衡转变，跨城流动性特征突显，加速空间对接与同城化进程。

Comprehensive evaluation and comparative analysis of accessibility in the four vertical and four horizontal HSR networks in China

Some limitations exist in the traditional methods of measuring accessibility, such as lacking comprehensive and comparative analysis from various aspects. Therefore, in this study,the evaluation of accessibility is conducted with three indicators, i.e. weighted average me,economic potential, and accessibility gravity center. After the evaluation, dynamic changes of urban accessibility with and without high- speed rail (HSR) are analyzed by ArcGIS method.Then comprehensive variable coefficient, hierarchy analysis and improved Huff model are used to nalyze spatial evolution characteristics and regularity of cities and regions along the HSR. Finally, the comprehensive accessibility of various HSR lines (nine HSR lines are involved in this study) is evaluated with Entropy-weight method, based on the accessibility system which is nstructed with six indicators, i.e. Ai, Pi, Ci, D- Value, CV and Pij. Results show that the comprehensive accessibility of various HSR lines is ifferent, with the order of their comprehensive strength as follows: Beijing- Guangzhou > Beijing- Shanghai > Shanghai- Kunming > Hangzhou-Shenzhen > Shanghai-Chengdu > Harbin-Dalian > Qingdao-Taiyuan > Zhengzhou- Xi'an > Lanzhou- Urumqi. The accessibility shows a decreasing trend from the eastern and central regions via the northeastern region to the western region. The accessibility of vertical HSR lines is better than the horizontal HSR lines. The increasing rate of economic potential is significantly higher than the decreasing rate of weighted average travel time. The movement of accessibility gravity center results in the spreading and overlapping of different time circles. The HSR spatial linkage mode of "core- core" has gradually developed into the mode of "core- network". "Four national service centers", i.e. Shanghai, Beijing, uangzhou and Shenzhen, and "six large regional service centers", i.e. Tianjin, Wuhan, Chongqing,Nanjing, Hangzhou and Shenyang have emerged in the HSR network and "multi-center" HSR service patterns and increasingly complicated spatial clusters have been formed. Affected by the HSR network, the gradual change and remodeling of regional spatial pattern have become more and more complicated. Spatial pattern in the "T-shaped" axes presents an evolving trend of polarization to equilibrium and intercity flows accelerate the process of spatial integration.