The nation's first subway to cross the Yangtze River started running in Wuhan, the capital of Central China's Hubei province, at 10 am on Friday.

Trains take only three minutes to run under the country's longest waterway. They have an average speed of 36 km per hour, with 26 trains scheduled to run every six minutes.

Passengers check the route map of the first subway of Wuhan, capital of Hubei province, on Friday. The line, which started operation on Friday, is the country's first subway to cross the Yangtze River. [Chen Zhuo/For China Daily]

Wuhan subway's Line 2, which links the city's two major downtown areas — Wuchang and Hankou — spans 27.73 km and has 21 stations. It takes about 50 minutes for trains to travel the line.

The line is expected to move 500,000 passengers a day, half of the city's cross-Yangtze traffic flow, and ease traffic congestion on the bridge over the river.

Huang Ming, who lives in Wuchang but works in Hankou, said the subway is extremely convenient for him.

"The bus from home to work takes two hours, and the situation worsens in bad weather or traffic jams," he said. "I will use the subway, which only takes around 30 minutes."

Construction of the subway, which started in February 2008, cost about 14.9 billion yuan ($2.4 billion), according to previous reports.

The most difficult part of the construction was building the underwater tunnel, said Lin Wenshu, manager in charge of construction at Wuhan Metro Group Construction.

"The geographic situation under the Yangtze River is very complicated," Lin said. "In order to ensure safety, we took a lot of protective measures and used a large number of skilled workers to prevent ground collapses and avoid underground gases."

Lin said the cross-river tunnel is about 3,000 meters long and includes five escape routes.

The 6,300-km Yangtze River, which originates in Northwest China's Qinghai province and traverses 10 provinces and municipalities before flowing into the East China Sea, is a major transport link between western and eastern China.

Yang Yao in Beijing and Xinhua contributed to this story.