A train makes a trial run on Sunday across the Qingjiang Bridge in the Enshi Tujia-Miao autonomous prefecture of Central China's Hubei province. Tian Daiming / Xinhua

BEIJING - The Yichang-Wanzhou railway, which goes through some of the most difficult terrain in the country and is considered one of China's most expensive rail projects, will begin operations on Wednesday, though the line will not become fully operational until Jan 11, said Guo Bing, an official of the Yichang section of the Wuhan Railway Bureau.

The maiden journey on the line will depart from Yichang city of Hubei province on Wednesday morning and arrive two hours later in Wanzhou district of Chongqing municipality.

The railway will cut the travel time between Chongqing and the central industrial hub of Wuhan in Hubei province from 22 hours to just five hours. Journeys from other central or eastern Chinese cities to Southwest China will also be greatly reduced, railway officials said.

A 22.57 billion yuan ($3.4 billion) project, the 377-kilometer railway features 253 bridges and 159 tunnels, including 34 that run through karst topography, or landscape formed by the dissolution of soluble rocks. The length of track that runs through bridges and tunnels is 278 km, or 73 percent of the line's total length.

"It was the hardest project I have ever worked on," Hu Ziping, the railway's chief designer, told China Daily.

Initially begun in 1909, the project was repeatedly abandoned due to technical problems, until the central government decided to relaunch it in 2003.

"Karst collapse was something we worried about the most," Hu said.

Engineers and workers took seven years to complete the railway, which runs along a stretch of mountains on the eastern edge of the Yunnan-Guizhou Plateau. In one of the most difficult phases of the project, it took nearly six years to drill a tunnel for the route through the Qiyue Mountain.

Hu said the railway's designed speed in 2003 was 160 km per hour - the fastest for its time. "It seems much slower now in this high-speed age," he said.

The Yichang-Wanzhou Railway is China's most expensive railway in terms of cost per km.

It cost about 60 million yuan to build each km of the railway, compared to 29 million yuan for each km of the Qinghai-Tibet Railway, which began operations in 2006.

Officials hope the trains will open up new opportunities for residents who live in the steep and remote Wuling Mountains.

Xinhua contributed to this story.