Final tests have begun on the Shanghai leg of the Beijing-Shanghai high-speed rail track, in preparation for its opening this summer, Xinhua reported. The testing of a 645-kilometre stretch of track, designed for trains travelling over 350km/h, is due to be completed in May to ensure a smooth opening of the entire link in June. It extends from the Zaozhuang West station in Shandong to Hongqiao station in Shanghai, via Nanjing, Jiangsu province. Testing will cover the new generation of high-speed bullet trains, the train operation system at 400km/h, its power supply system and its concrete-based, ballastless track structure, which reduces noise and pollution. When it opens, the 1,318-kilometre, 220.9 billion yuan (HK$261 billion) line will become the world's longest single high-speed rail connection. Xinhua reported that the service would cut travel time between Shanghai and Beijing to four hours - less than half the time taken by the fastest trains today. Construction workers tightened the last bolt on the track in November, more than 21/2 years after the mammoth project began. A test run was conducted at 486.1 km/h in December, setting a speed record. All of this paves the way for its June opening. Railway officials estimate the 24-station route - serving Beijing, Tianjin and Shanghai municipalities and seven provinces - will transport a total of 160 million passengers a year. The high-speed era in China opened with the 117km line between Beijing and Tianjin on August 1, 2008. Since then, a massive drive has been launched to upgrade and modernise the network. The Ministry of Railways aims to have 25,000 kilometres of newly built high-speed track by 2015, according to the ministry's chief planner, Zheng Jian . That will expand the national rail network to 120,000 kilometres by 2015 - an increase of more than 30 per cent over the 91,000 kilometres now in use.