Group 1 - The core viewpoint of the article highlights the growth and changes in urban rail transit systems across major Chinese cities, with a specific focus on Nanjing's rising ranking in operational mileage [3][4]. - As of December 31, 2025, a total of 54 cities in China will have 343 urban rail transit lines in operation, covering 11,710.3 kilometers and 6,680 stations, with an addition of 18 new lines and 764.7 kilometers of new operational mileage in 2025 [2]. - Beijing continues to lead the nation in urban rail transit operational mileage, with 30 lines and 909 kilometers, while Nanjing has moved up to the seventh position, surpassing Hangzhou and Chongqing, due to the opening of new lines [4]. Group 2 - Several major cities are set to open new rail transit lines this year, including Beijing's first interprovincial line, which will span approximately 81.2 kilometers, and Shanghai's line expected to be operational by the end of the year [5]. - Nanjing is preparing for the opening of two lines, the 6th line and the Ningma line, which will connect Jiangsu and Anhui provinces, with the 6th line measuring about 32.35 kilometers and the Ningma line about 54.23 kilometers [5]. - The urban rail transit landscape is expected to continue evolving as cities announce progress on ongoing projects, potentially leading to further changes in rankings by the end of the year [6].

重庆轨道交通15号线建设取得突破，二期控制性工程中梁山隧道顺利贯通。该隧道全长4944米，地质结 构复杂，施工过程中需穿越富水区、岩溶发育区和煤矿采空区等，中铁十四局采用超前地质预报等技 术，确保安全穿越风险区域。15号线设计时速140公里，分两期建设，二期全长约33公里，设11座车 站，开通后将缓解现有轨道线路客流压力，完善重庆市轨道交通网络。(央视新闻) ...