Chongqing Rail Transit

The Chongqing Rail Transit (branded as CRT; also known as Chongqing Metro) is the rapid transit system in the city of Chongqing, China. In operation since 2005, it serves the transportation needs of the city's main business and entertainment downtown areas and inner suburbs. As of December 2023, CRT consisted of eleven lines, with a total track length of 523.68 km (325 mi). Lines 1, 4, 5, 6, 9, 10, 18, the Loop line and Jiangtiao line are conventional heavy-rail metro lines, while Lines 2 and 3 are high-capacity monorails. To keep up with urban growth, construction is under way on Line 18 and several other lines, in addition to extensions to Lines 5, 6 and 10.

The Chongqing Rail Transit is a unique transit system in China because of the geography of Chongqing being a densely-populated but mountainous city, with multiple river valleys. Two lines use heavy-monorail technology, leveraging the ability to negotiate steep grades and tight curves and rapid transit capacity. They are capable of transporting 32,000 passengers per hour per direction. However the busiest section of Line 3 reaches a peak passenger volume of 37,700 pphpd in 2019. At 98 km (61 mi), the system's two monorail lines form the longest monorail system in the world, with the 56.1 km (34.9 mi) Line 3 being the world's longest single monorail line even if the 11.0 km (6.8 mi) Konggang branch is excluded. The length and the capacity of its monorail network both also make it the world's busiest monorail system, with a total of 94 million and 250 million rides in 2015 on Line 2 and Line 3, respectively. The latter ridership statistic for Line 3 also makes it the world's busiest single monorail line.

The extreme difference in elevation between the river valleys and the hilly plateaus of Chongqing pose a unique challenge in designing alignments for conventional rail transit lines. The network currently has the world's highest metro-only bridge, the Caijia Rail Transit Bridge for Line 6, spanning the Jialing River valley, with the bridge deck being approximately 100 m (328 ft) above the water. Hongyancun station is the deepest metro station in China and the deepest metro station in the world with the station reaching 116 m (381 ft) below the surface, surpassing the Kyiv Metro's Arsenalna station. Hongtudi station and Liyuchi station, both on Line 10, are the second and third deepest stations in China, being 94 m (308 ft) and 76 m (249 ft) below the surface respectively. Additionally, Hualongqiao station is a six story structure that has Line 9 trains stopping 48 meters above the surface, making it the tallest metro station in the world, surpassing Smith–Ninth Streets station in New York.

The Chongqing Rail Transit system possesses a number of extremely-long metro-only bridges. The 1,650 m (5,413 ft) long Egongyan Rail Transit Bridge carries the southern arc of the Loop line across the Yangtze River using a 600 m (1,969 ft) long suspension main span, making it the longest metro-only suspension bridge by main span in the world. The Nanjimen Bridge carries Line 10 trains across a 1,225 m (4,019 ft) cable-stayed bridge with a main span of 480 m (1,575 ft), making it the longest metro-only cable-stayed bridge by main span in the world. The Gaojia Huayuan Jialing River Rail Transit Bridge carries the western arc of the Loop line over the Jialing River using a long 594 m (1,949 ft) bridge with a main span of 340 m (1,115 ft). Additionally, Chongqing Rail Transit system has numerous double-deck bridges carrying vehicle and metro traffic, such as the Chaotianmen Bridge, which is the world's longest arch bridge.