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].

Group 1 - The construction of seven metro lines in Nanjing has made significant progress as of the end of December [1][3] - The second phase of Line 4 has commenced construction on four stations and a central ventilation shaft, with three stations and a shaft having completed their main structure [1] - For Line 6, project acceptance has been achieved, and it is currently undergoing non-passenger test runs [1] Group 2 - The first phase of Line 9 has completed all main structures, with auxiliary structure construction ongoing [3] - A total of 31 shield tunnels have started, with 30 of them already completed [3] - The first phase of Line 11 has seen 18 stations commence construction, with 17 stations having completed their main structures [3] Group 3 - The Ningma Line has passed project acceptance and is currently in non-passenger test runs [3] - The Ningchao Line (Nanjing section) is advancing preliminary construction preparations for the underground section, while the elevated section is progressing with civil engineering [3] - The Ningyang Line (Nanjing section) has three stations and three elevated sections under construction, with two stations having completed protective structures and one station completing its main structure [3]

Group 1 - Nanjing Metro Line 6 and Ningma Line have passed project engineering acceptance [1]