China’s New Under-River Rail Tunnel to Slash Travel Times Across Yangtze Corridor

China has finished building two tunnels for high-speed rail underneath the Yangtze River, which is part of a China Railway project to build a high-speed rail line from Shanghai to Chongqing to Chengdu.

With the whole corridor completed, travel time between Shanghai and Chengdu will be lowered to around 6.7 hours from over 12 hours, and that between Shanghai and Chongqing will be lowered to around 5.3 hours.

The projects alleviate a critical bottleneck in the transportation system along the Yangtze, which is the busiest of China’s rivers, by enabling trains to cross at speeds of up to 350 km per hour.

The tunnels also help to enable China’s larger goal of making the Yangtze River Economic Belt more connected, while causing the least possible disruption to river traffic and protected aquatic habitats.

Connecting Shanghai on China’s east coast with the southwestern cities of Chongqing and Chengdu, the tunnels are part of a rail line that stretches about 2,100 kilometers (1,300 miles) through China. It is thought to enhance travel for passengers and goods, and economic activity in over 20 cities.

Faster Journeys Across the Yangtze

The Shanghai-Chongqing-Chengdu high-speed railway will have a significant impact on travel time between major cities on the Yangtze corridor. Trains between Shanghai and Chengdu usually take over 10 hours due to these trains’ indirect routes.

The total line will take about 6.7 hours when it is completed, and the time between Shanghai and Chongqing will be shortened to about 5.3 hours.

The tunnels will allow trains to pass through uninterrupted under the river at speeds of up to 350 km/h, says China Railway Group. The underwater alignment allows trains to operate at high speed, which is not possible with many of the existing Yangtze crossings utilizing speed-restricted bridges due to curves.

Engineers selected tunnels instead of bridges because the Yangtze is one of China’s busiest inland shipping routes. The underwater design also reduces the impact on environmentally protected areas and aquatic ecosystems along the river.

Two Major Tunnel Projects

The two projects are the Chongming-Taicang Yangtze River Tunnel, between Chongming District in the city of Shanghai and Taicang in neighboring Jiangsu province, and the second tunnel project, which will link the Pingxi District with the Xinyang District in the city of Huzhou, also in Jiangsu province.

The tunnel, which is 14.25km long, including over 11km underground, finished its undersea dig on March 29, after almost two years. The excavation was performed by the shield tunnelling machine “Linghang,” said China Railway Group.

It also forms part of the Shanghai-Nanjing line of the Shanghai-Chongqing-Chengdu high-speed rail line, and will eventually be included in China’s national “eight vertical and eight horizontal” high-speed rail network.

The second project is the 11.9-km-long Caiyuanba Yangtze River Railway Tunnel (RRRT), which was completed on July 25 in Chongqing. The tunnel links two districts in the southwestern municipality, and will be part of a high-speed rail line that goes from Chongqing to Xiamen in Fujian province.

China Railway 14th Bureau Group, the contractor behind the project, employed a specially designed tunnel boring machine, Changjiang, to bore through alternating rock layers under the river under high water pressure, Xinhua state news agency reported.

Economic Impact Beyond the Endpoints

The railway’s advantages are believed to go beyond the cities of Shanghai, Chongqing and Chengdu. The entire corridor could be expected to create an extra 1.5 trillion yuan ($209 billion) in industrial value, China Central Television reported, and to provide economic support for over 20 cities along the way.

The Yichang-Xingshan segment is already in trial operation, and the second segment between Xingshan and Xianfeng will be opened for public use later this year.

After being fully connected, it should be able to shorten the way between Yichang and Chongqing to less than 3 hours and also connect the Guanzhong Plain and the middle part of the Yangtze River with the Chengdu-Chongqing metropolitan area directly via high-speed rail.

Part of China’s Expanding High-Speed Rail Network

The line from Shanghai to Chongqing to Chengdu is one of China’s biggest transportation initiatives, running more than 2,000 km, and costing over 500 billion yuan ($72.8 billion). The project has been added to major priorities of the 15th Five-Year Plan from 2026 to 2030 in China.

The construction of China’s “eight vertical and eight horizontal” high-speed rail project had reached approximately 84% of its completion by March, said China Railway Group.

As the network continues to grow, it will enhance connectivity between key city clusters and facilitate faster journeys over short and long distances, said Yu Jian, an expert at the China Railway Economic and Planning Research Institute, in a statement in December 2025.

The opening time of the Chongming-Taicang tunnel and the Caiyuanba tunnel has not been confirmed. Their services will start only when the rest of their respective rail lines are finished, and the line from Shanghai to Chongqing-Chengdu will be one of China’s speediest east-west high-speed rail lines.