Two engineers test seats in a business-class car of a CRH380B high-speed train in Changchun, Jilin province. [Wang Haofei/Xinhua]

The high-speed railway linking Beijing to Shanghai, which will open later this month, is safe and reliable and the reduction in operating speed is to maximize efficiency, rail authorities say.

"Its technology is advanced, its quality reliable and safety guaranteed. It is completely ready for operation and will open in late June," Hu Yadong, vice-minister of railways, told a news conference on June 13.

Tickets for the journey between China's top two cities will range from 410 yuan to 1,750 yuan (44 euros to 187 euros), depending on the train's designated speed and seat category. Tickets will be sold online a week before the formal launch date.

The 1,318-km line will run 90 pairs of trains daily. These will travel at either 300 km/h or 250 km/h. The fastest travel time between the two cities will be four hours and 48 minutes, or about half the time trains currently take.

The ministry had previously considered cutting the travel time to just four hours by running trains at a top speed of 380 km/h.

Speed cuts will also be introduced on other rail routes.

Starting July 1, several high-speed railways, including the lines linking Wuhan and Guangzhou, Zhengzhou and Xi'an, and Shanghai and Nanjing, will see train speeds reduced from 350 km/h to 300 km/h. Trains that run at 250 km/h will be added to these lines to meet diversified needs.

The speed cut is in line with a nationwide directive made public in April that said all high-speed trains must run at a slower pace than previously announced - no faster than 300 km/h - to make journeys safer.

The directive followed a major corruption scandal in February when then railways minister, Liu Zhijun, was dismissed after an investigation into serious disciplinary violations. It raised concerns over the costs and safety of high-speed rail links.

Hu rejected speculation that operating speed had been slashed because high-speed railways were unsafe or unreliable. He said that the decision was due to maximizing efficiency. The high-speed railway was built according to the technical standards of travel at 350 km/h, and all test runs were conducted at 350 km/h, he said.

During the test period, from November to May 10, trains covered a length of more than 600,000 km, and a one-month trial operation that commenced on May 11 has seen trains covering a total length of 2 million km.

The technical reliability of the line, as measured by international criteria, is world class, he said. "But when we decided on its commercial operating speed, we took into account economic efficiency."

The vice-minister said that the railway will operate a dual-speed system with the slower trains making way for faster ones. The bigger the speed gap (between two types of trains), the greater the impact on the line's operating efficiency, he said.

The ministry found that running trains at 350 km/h and 250 km/h on the same line will be 20 percent less efficient than operating trains traveling at 300 km/h and 250 km/h.

The ministry also took energy consumption, the wear and tear on tracks and rolling stock, into consideration, Hu said.

The ministry is taking every measure to ensure the line's safety.

Maintenance workers will spend four hours checking the tracks every night. Two passenger-free trains will travel the line every morning to conduct safety checks before trains with passengers get the green light.